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Python 2.4 Quick Reference Card

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Python 2.4 Quick Reference Card
©2005-2007 — Laurent Pointal — License CC [by nc sa]
Environment Variables........................1 Command-line Options....................... 1 Files Extensions.................................. 1 Language Keywords............................1 Builtins................................................1 Types.................................................... 1 Functions.............................................. 1 Statements......................................... 1 Blocks....................................................1 Assignment Shortcuts...........................1 Console & Interactive Input/Output.... 2 Objects, Names and Namespaces...... 2 Identifiers..............................................2 Objects and Names, Reference Counting............................................... 2 Mutable/Immutable Objects..................2 Namespaces......................................... 2 Constants, Enumerations......................2 Flow Control........................................2 Condition...............................................2 Loop...................................................... 2 Functions/methods exit.........................2 Exceptions............................................ 2 Iterable Protocol....................................2 Interpretation / Execution................... 2 Functions Definitions & Usage............ 2 Parameters / Return value....................2 Lambda functions................................. 2 Callable Objects.................................... 2 Calling Functions...................................3 Functions Control..................................3 Decorators............................................ 3 Types/Classes & Objects.....................3 Class Definition.....................................3 Object Creation.....................................3 Classes & Objects Relations..................3 Attributes Manipulation.........................3 Special Methods....................................3 Descriptors protocol..............................3 Copying Objects....................................3 Introspection.........................................3 Modules and Packages........................3 Source encodings..................................3 Special Attributes..................................3 Main Execution / Script Parameters....4 Operators............................................4 Priority.................................................. 4 Arithmetic Operators............................ 4 Comparison Operators..........................4 Operators as Functions.........................4 Booleans............................................. 4 Numbers............................................. 4 Operators..............................................4 Functions.............................................. 4 Bit Level Operations........................... 5 Operators..............................................5 Strings................................................ 5 Escape sequences.................................5 Unicode strings..................................... 5 Methods and Functions.........................5 Formating..............................................6 Constants..............................................6 Regular Expressions..............................6 Localization...........................................7 Multilingual Support..............................7 Containers.......................................... 8 Operations on Containers..................... 8 Copying Containers...............................8 Overriding Containers Operations........ 8 Sequences.......................................... 8 Lists & Tuples........................................8 Operations on Sequences..................... 8 Indexing................................................ 8 Operations on mutable sequences....... 8 Overriding Sequences Operations........ 8 Mappings (dictionaries).......................8 Operations on Mappings....................... 8 Overriding Mapping Operations............8 Other Mappings.....................................9 Sets.....................................................9 Operations on Sets................................9 Other Containers Structures, Algorithms.......................................... 9 Array..................................................... 9 Queue................................................... 9 Priority Queues..................................... 9 Sorted List.............................................9 Iteration Tools.......................................9 Date & Time........................................9 Module time..........................................9 Module datetime.................................10 Module timeit......................................10 Other Modules.....................................10 Files.................................................. 10 File Objects......................................... 10 Low-level Files.....................................10 Pipes................................................... 10 In-memory Files.................................. 10 Files Informations................................11 Terminal Operations........................... 11 Temporary Files.................................. 11 Path Manipulations..............................11 Directories...........................................11 Special Files........................................ 12 Copying, Moving, Removing............... 12 Encoded Files......................................12 Serialization........................................ 12 Persistence..........................................12 Configuration Files.............................. 12 Exceptions........................................ 12 Standard Exception Classes................12 Warnings.............................................13 Exceptions Processing........................ 13 Encoding - Decoding.........................13 Threads & Synchronization............... 13 Threading Functions........................... 13 Threads...............................................13 Mutual Exclusion.................................13 Events.................................................13 Semaphores........................................13 Condition Variables.............................13 Synchronized Queues......................... 13 Process............................................. 13 Current Process...................................13 Signal Handling...................................14 Simple External Process Control......... 14 Advanced External Process Control.... 15 XML Processing................................. 15 SAX - Event-driven..............................15 DOM - In-memory Tree....................... 16 Databases.........................................17 Generic access to DBM-style DBs....... 17 Standard DB API for SQL databases....17 Bulk...................................................18
Styles : keyword function/method type replaced_expression
variable literal module module_filename language_syntax
Notations :
f(��)�� return value f(��)➤ return nothing (procedure)
[x] for a list of x data, (x) for a tuple of x data, may have x{n}�� n times x data.
1 no case distinction in module��file mapping
1 = -d command-line option
PYTHONHOME Modify standard Python libs prefix and exec prefix locations. Use <prefix>[:<execprefix>]. PYTHONINSPECT
1 = -i command-line option
1 = -O command-line option
PYTHONPATH Directories where Python search when importing modules/packages. Separator : (posix) or ; (windows). Under windows use registry HKLM\Sofware\��. PYTHONSTARTUP File to load at begining of interactive sessions. PYTHONUNBUFFERE D
1 = -u command-line option
1 = -v command-line option 1 If set to non-empty value.
python [-dEhiOQStuUvVWx] [-c cmd | -m mod | file | -] [args] -d Output debugging infos from parser. -E Ignore environment variables. -h Print help and exit. -i Force interactive mode with prompt (even after script execution). -O Optimize generated bytecode, remove assert checks. -OO As -O and remove documentation strings. -Q arg Division option, arg in [old(default),warn,warnall,new]. -S Don't import site.py definitions module. -t Warn inconsistent tab/space usage (-tt exit with error). -u Use unbuffered binary output for stdout and stderr. -U Force use of unicode literals for strings. -v Trace imports. -V Print version number and exit. -W arg Emit warning for arg "action:message:category:module:lineno" -x Skip first line of source (fort non-Unix forms of #!cmd). -c cmd Execute cmd. -m mod Search module mod in sys.path and runs it as main script. file Python script file to execute. args Command-line arguments for cmd/file, available in
.py=source, .pyc=bytecode, .pyo=bytecode optimized, .pyd=binary
module, .dll/.so=dynamic library.
.pyw=source associated to pythonw.exe on Windows platform, to
run without opening a console.
List of keywords in standard module keyword.
and as1 assert break class continue def del elif else except exec finally for from global if import in is lambda not or pass print raise return try while yield
1 not reserved, but avoid to redefine it.
Don't redefine these constants : None, True, False.
Available directly everywhere with no specific import. Defined also in module __builtins__.
basestring1 bool buffer complex dict exception file float frozenset int list long object set slice str tuple type unicode xrange
1 basestring is virtual superclass of str and unicode.
This doc uses string when unicode and str can apply.
Constructor functions of builtin types are directly accessible in builtins.
__import__ abs apply1 callable chr classmethod cmp coerce compile delattr dir divmod enumerate eval execfile filter getattr globals hasattr hash help hex id input intern2 isinstance issubclass iter len locals map max min oct open ord pow property range raw_input reduce reload repr reversed round setattr sorted staticmethod sum super unichr vars zip
1 Use f(*args,**kargs) in place of apply(f,args,kargs). 2 Don't use intern.
One statement per line1. Can continue on next line if an expression or a string is not finished ( ( [ { """ ''' not closed), or with a \ at end of line. Char # start comments up to end of line.
Null statement.
assert expr[,message]
Assertion check expression true.
del name[,��]
Remove name �� object binding.
print [>>obj,][expr[,��][,]
Write expr to sys.stdout2.
exec expr [in globals [,
locals]] Execute expr in namespaces. fct([expr[,��]],
[name=expr [,��]] [,*args][,**kwargs])
Call any callable object fct with given arguments (see Functions Definitions & Usage - p2). name[,��] = expr Assignment operator3.
1 Multiple statements on same line using ; separator - avoid if not
2 Write to any specified object following file interface (write
method). Write space between expressions, line-return at end of line except with a final ,.
3 Left part name can be container expression. If expr is a sequence
of multiple values, can unpack into multiple names. Can have multiple assignments of same value on same line : a = b = c = expr.
Other statements (loops, conditions��) introduced in respective parts.
A : between statements defines dependant statements, written on same line or written on following line(s) with deeper indentation. Blocks of statements are simply lines at same indentation level. if x<=0 : return 1 if asin(v)>pi/4 : a = pi/2 b = -pi/2 else : a = asin(v) b = pi/2-a
Statement continuation lines don't care indentation. To avoid problems, configure your editor to use 4 spaces in place of tabs.
Assignment Shortcuts
a += b a -= b a *= b a /= b a //= b a %= b a **= b a &= b a |= b a ^= b a >>= b a <<= b Evaluate a once, and assign to a the result of operator before = 1a 1b 1c

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applied to current a and b. Example : a%=b �� a=a%b
print expression[,��]
input([prompt]) �� evaluation of user input (typed data) raw_input([prompt]) �� str: user input as a raw string
Direct manipulation (redefinition) of stdin/stdout/stderr via sys module :
sys.stdin sys.stdout sys.stderr sys.__stdin__ sys.__stdout__ sys.__stderr__
All are files or files-like objects. The __xxx__ forms keep access to original standard IO streams.
Ctrl-C raises KeyboardInterrupt exception. _ �� value of last expression evaluation
help([object]) ➤ print online documentation
sys.displayhook �� (rw) fct(value) called to display value sys.__displayhook__ �� backup of original displayhook function sys.ps1 �� str: primary interpreter prompt sys.ps2 �� str: secondary (continuation) interpreter prompt
See external package ipython for an enhanced interactive Python shell.
Use : [a-zA-Z_][a-zA-Z0-9_]* Special usage for underscore : _xxx global not imported by import * _xxx implementation detail, for internal use (good practice) __xxx 'private' class members, defined as _ClassName__xxx __xxx__ normally reserved by Python Case is significant : This_Name != THIS_NAME.
Objects and Names, Reference Counting
Data are typed objects (all data), names are dynamically bound to objects. = assignment statement bind result of right part evaluation into left part name(s)/container(s). Examples : a = 3*c+5 s = "Hello" a,b = ("Hello","World") pi,e = 3.14,2.71 x,y,tabz[i] = fct(i) a,b = b,a When an object is no longer referenced (by names or by containers), it is destroyed (its __del__ method is then called).
sys.getrefcount(object)�� int: current reference counter of object
Standard module weakref define tools to allow objects to be garbage collected when necessary and dynamically re-created on- demand.
Mutable/Immutable Objects
Mutable objects can be modified in place. Immutable objects cannot be modified (must build a new object with new value). Immutable : bool, int, long, float, complex, string, unicode,
tuple, frozenset, buffer, slice.
Mutable : list, set, dict and other high level class objects. There is no constant definition. Just use uppercase names to identify symbols which must not be modified.
Places where Python found names. Builtins namespace �� names from module __builtins__, already available. Global namespace �� names defined at module level (zero indentation). Local namespace �� names defined in methods/functions.
del name ➤ remove existing name from namespace (remove object
globals() �� dict: identifier��value of global namespace locals() �� dict: identifier��value of local namespace
Current scope �� names directly usable. Searched in locals, then locals from enclosing definitions, then globals, then builtins. Out-of-scope name �� use the dotted attribute notation x.y (maybe
x.y.z.t)�� where x is a name visible within the current scope.
Class namespace �� names defined in a class (class members). Object namespace �� names usable with object.name notation (attributes, methods). Namespaces can be nested, inner namespaces hidding identical names from outer namespaces.
dir([object]) �� list: names defined in object namespace1 vars([object]) �� dict2: identifier:value of object as a namespace1
1 if object not specified use nearest namespace (locals). 2 must not be modified.
Constants, Enumerations
Use uppercase and _ for constants identifiers (good practice). May define namespaces to group constants. Cannot avoid global/local name redefinition (can eventually define namespaces as classes with attributes access control - not in Python spirit, and execution cost). See third party modules pyenum for strict enum-like namespace.
if cond : inst
[ elif cond : inst ] [ else : inst ]
There is no 'switch' or 'case'. Can use if elif elif�� else. Can use a mapping with functions bound to cases.
for var[,��] in iterable : inst
[ else : inst ]
while cond : inst
[ else : inst ]
Exit loop with break. Go to next iteration with continue.
Loops else blocs only executed when loop exit normally (without break).
Functions/methods exit
Exit function/method with return [value] Exit from generator body with yield value
Multiple returned values using tuple data. Cannot yield within a try/finally block.
try : inst except [ except_class [,value ]] : inst
[ else : inst ]
Can have a tuple of classes for except_class. Not specifying a class catch all exceptions. Block else executed when try block exit normally.
try : inst finally : inst
Process finally block in all execution paths (normal or exception).
raise exception_class[,value[,traceback]] raise exception_object raise
Last form re-raise the currently catched exception in an exception handler.
Iterable Protocol
Generic and simple protocol allowing to iterate on any collection of data. Objects of class defining __iter__ or __getitem__ are iterable (directly usable in for loops).
__iter__(self) �� iterator on self iter(object) �� iterator on iterable object iter(callable,sentinel) �� iterator returning callable() values up to
enumerate(iterable)�� iterator returning tuples (index,value) from iterable Iterators Objects Interface next(self)�� next item1 __iter__(self)�� iterator object itself
1 When reach end of collection, raise StopIteration exception on
subsequent calls (ie. iterator usable only one time on a collection).
Functions retaining their state between two calls. Return values using yield. Stop generation via simple return or via raise
1) build generator from function : gen=generatorfct(args) 2) use gen.next() values until StopIteration is raised. Generator iterable expressions with : (x for x in iterable where cond)
Operations with/on Iterable
See Operations on Containers (p8). See Iteration Tools (p9).
compile(string1,filename,kind2[,flags3[,dont_inherit3]]) �� code object eval(expression[,globals[,locals]]) �� value: evaluation4 of expression
eval(code_object[,globals[,locals]]) �� value: evaluation4 of code_object
statements [in globals[,locals]] ➤ statements string1 executed4
execfile(filename[,globals[,locals]]) ➤ file filename interpreted4
1 Multi-line statements in source code must use \n as newline, and
must be terminated by a newline.
2 Kind relative to string content, 'exec' �� sequence of statements,
'eval' �� single expression, 'single' �� single interactive
3 Flags and dont_inherit are for future statements (see doc). 4 In context of globals and locals namespaces. 5 Exec is a langage statement, others are builtin functions.
def fctname([paramname[=defaultvalue][,��]] [,*args][,**kwargs]) :
new.function(code,globals[,name[,argdefs]]) �� python function (see
Parameters / Return value
Parameters are passed by references to objects.
You can modify values of mutable objects types. You cannot modify values of immutable objects types - as if they were passed by value.
Notation * �� variable list of anonymous parameters in a tuple. Notation ** �� variable list of named parameters in a dict. Return value(s) with return [value[,��]] For multiple values, return a tuple. If no return value specified or if end of function definition reached, return None value.
Lambda functions
lambda param[,��] : expression
Anonymous functions defined inline. Result of expression evaluation is returned (it must be an expression, no loop, no condition).
Expression uses values known at definition time (except for params).
Callable Objects
Objects having a __call__ method can be used as functions. Methods bound to objects can be used as functions : f = o.meth
callable(x) �� bool: test x callable with x(��)
2a 2b 2c

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Calling Functions
[name=] fctname([expr[,��]][,name=expr[,��][,*args][,**args])
Anonymous parameters passed in parameters order declaration. Params having default value can be omitted. Notation * �� pass variable list of anonymous parameters in a
Notation ** �� pass variable list of named parameters in a dict.
Functions Control
sys.getrecursionlimit()�� int: current recursion limit for functions sys.setrecursionlimit(limit) ➤ set recursion limit for functions
Glue code (functions) called at functions and methods definitions time, return the final function/method (generally with wrapping code). @decoratorname [(decorator_arguments)] [��]
def fct(fct_rguments):��
@dec1 @dec2(args) @dec3
def fct(��):��

def fct(��):��
fct = dec1(dec2(args)(dec3(fct))))
See page PythonDecoratorLibrary in python.org Wiki for some decorators definitions.
All data are typed objects relying to classes.
type(o) �� type: type object of o
Standard module types define type objects for builtins types.
Class Definition
class classname [(parentclass[,��])] :
varname = expr ➤ varname defined in classname namespace
def metname(self[,��]): ➤ define methods like functions
Support multiple inheritance. Can inherit from builtin class. Inherit at least from object base class => Python 'new style class'. First parameter of methods is target object, standard use self name. Access class members via class name, object members via self.
This doc consider you use new style class (inheriting from object).
new.classobj(name,baseclasses,dict) �� new class (see docs) new.instancemethod(fct,instance,class) �� new method: bound to
instance it it is not None, see docs
Class definition create a new type. It can be done 'by hand' with : x = type('classname',(parentclass,[��]),{varname:expr[,��]}
def metname(self[,��]):
x.metname = metname This allow creation of metaclass class (class building other class).
Object Creation
obj = ClassName(initargs��)
In case of exception during initialization, object is destroyed when exiting init code (reference counter reach zero).
new.instance(class[,dict]) �� object: create new class instance without
calling __init__ method, dict is initial object attributes
Classes & Objects Relations isinstance(obj,classinfo) �� bool: test object kind of type/class
issubclass(aclass,aparent) �� bool: test same class or parent
Prefer isinstance() to type() for type checking.
Parent class methods are not automatically called if overriden in subclass - they must be explicitly called if necessary. Call parent methods via super function :
Or the old way, via parent class namespace : ParentClass.methodname(self,args��)
Attributes Manipulation
object.name = value
setattr(object,name,value) ➤ object attribute set to value
object.name �� value of object attribute
getattr(object,name[,default])�� value of object attribute
del object.name
delattr(object,name) ➤ object attribute removed Special Methods
Other special overridable __xxx___ methods are listed in respective sections.
Object Life __new__(classref,initargs��)�� object of classref type, already
__init__ (self,initargs��)➤ called to initialize object with initargs __del__ (self)➤ called when object will be destroyed
1 If don't return a classref object, then object.__init__ is called with
Object Cast __repr__(self)�� str: called for repr(self) and `self` __str__(self) �� str: called for str(self) and print self __coerce__(self,other) �� value, called for coerce(self,other) Object Hash Key __hash__(self)�� int: 32 bits hash code for object, used for hash(obj)and quick dict mapping keys comparison - default
implementation use hash(id(self))
Attributes access
See also "Descriptors protocol" infra.
__getattr__(self,name)�� value, called for undefined attributes __getattribute__(self, name)�� value, always called __setattr__(self, name, value) ➤ called for obj.name=value __delattr__(self, name) ➤ called for del obj.name __call__(self, *args, **kwargs)�� value, called for obj(��) Static method / Class method
Use standard decorators (see Decorators p3).
class ClassName :
def methodname(��): ��
def methodname(classref,��): ��
Descriptors protocol
Descriptors are attribute objects controling access to attributes values. They must define some of following methods :
__get__(self,obj,ownerclass)�� attribute value for obj __set__(self,obj,value) ➤ modify attribute in obj, set to value __delete__(self,obj) ➤ remove attribute from obj
In these methods self is the descriptor object, and obj is the target object which attribute is manipulated.
A descriptor to directly bind methods/functions to control attribute access. Use builtin type property with init args.
class MyClass :
attributename = property(getter,setter,deleter,description)
Each init arg default to None (ie. undefined).
Copying Objects
Assignment only duplicate references. To shallow copy an object (build a new one with same values - referencing same content), or to deep copy an object (deep-copying referenced content), see object copy methods, and functions in standard module copy.
copy.copy(object)�� value: shallow copy of object copy.deepcopy(object[[,memo],_nil])�� value: deep copy of object1
1 Params memo and nil are used in recursive deepcopy, their
default values are None and empty list.
Copy Protocol __copy__(self)�� value: shallow copy of self, called by
__deepcopy__(self,memo)�� value: deep copy of self, called by
For copying, objects can define pickling protocol too (see Files - Serialization - p12), in place of __copy__ and __deepcopy__.
Beyond this documentation. Many __xxx___ attributes are defined, some are writable (see other docs). See standard module inspect to manipulate these data.
Example of Introspection Attributes
Note: classes are objects too!
__base__ �� list: parent classes of a class __slots__ �� tuple: allowed objects attributes names1 of a class __class__ �� class/type: object's class __dict__ �� dict: defined attributes (object namespace) of an instance __doc__ �� string: documentation string of a package, module, class,
__name__ �� str: object definition name of a function __file__ �� string: pathname of loaded module .pyc, .pyo or .pyd
1 List of allowed attributes names. Usage discouraged.
File gabuzo.py ➤ module gabuzo. Directory kramed/ with a file __init__.py ➤ package kramed. Can have sub-packages (subdirectories having __init__.py file). Searched in the Python PATH. Current Python PATH stored in sys.path list. Contains directories and .zip files paths. Built from location of standard Python modules,
PYTHONPATH environment variable, directory of main module given
on command line, data specified in lines of .pth files found in Python home directory, and data specified in registry under Windows. Current list of loaded modules stored in sys.modules map (main module is under key __main__).
import module [as alias ] [,��] from module import name [as alias ] [,��] from module import *
reload(module) module is reloaded (but existing references still refer
old module content)
new.module(name[,doc]) �� new module object.
Import can use package path (ex:from encoding.aliases
Direct import from a package use definitions from __init__.py file. Very careful with import * as imported names override names already defined. To limit your modules names exported and visible by import *, define module global __all__ with list of exported names (or use global names _xxx).
See __import__ builtin function, and modules imp, ihooks.
__import__(modulename[, globals[,locals[,lnameslist]]]) Source encodings
See PEP 263. Declare source files encoding in first or second line in a special comment.
# -*- coding: encoding_name -*-
If this is not specified, Python use sys.getdefaultencoding() value (see modules sitecustomize.py and user.py).
It is important to specify encoding of your modules as u"��" strings use it to correctly build unicode literals.
Special Attributes
__name__ �� str: module name, '__main__' for command-line called
script 3a 3b 3c

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__file__ �� string: pathname of compiled module loaded
The 'main' module is the module called via command-line (or executed by shell with first script line #! /bin/env python). Command-line parameters are available in sys.argv (a python
At end of module, we may have : if __name__=='__main__' :
# main code # generally call a 'main' function:
# or in lib modules, execute test/demo code...
Execution exit after last main module instruction (in multithread, wait also for end of non-daemon threads), unless interactive mode is forced. Can force exit with calling sys.exit(code), which raise a
SystemExit exception - see Current Process - Exiting (p13).
Deal with arithmetic, boolean logic, bit level, indexing and slicing.
1 ( a,��) [ a, ��]
{a:b,��} ` ��`
6 x +y
x -y
11 x <y x<=y x >y x>=y x==y x!=y
x <>y x is y x is not y x in s x not in s
2 s[i] s[i:j]
s .attr f(��)
7 x<<y
12 not x 3 + x - x ~x 8 x &y 13 x and y 4 x**y 9 x ^y 14 x or y 5 x *y x /y x %y 10 x |y 15 lambda args:expr
Arithmetic Operators
Can be defined for any data type.
Arithmetic Overriding __add__(self,other) �� value: called for self + other __sub__(self,other) �� value: called for self - other __mul__(self,other) �� value: called for self * other __div__(self,other) �� value: called1 for self / other __truediv__(self,other) �� value: called2 for self / other __floordiv__(self,other) �� value: called for self // other __mod__(self,other) �� value: called for self % other __divmod__(self,other) �� value: called for divmod(self,other) __pow__(self,other) �� value: called for self ** other __nonzero__(self)�� value: called for nonzero(self) __neg__(self) �� value: called for -self __pos__(self) �� value: called for +self __abs__(self) �� value: called for abs(self) __iadd__(self,other) ➤ called for self += other __isub__(self,other) ➤ called for self -= other __imul__(self,other) ➤ called for self *= other __idiv__(self,other) ➤ called1 for self /= other __itruediv__(self,other) ➤ called2 for self /= other __ifloordiv__(self, other) ➤ called for self //= other __imod__(self,other) ➤ called for self %= other __ipow__(self,other) ➤ called for self **= other
1 without / 2 with from __futur__ import division
Binary operators __xxx__ have also __rxxx__ forms, called when target object is on right side.
Comparison Operators
Operators can compare any data types. Compare values with < <= > >= == != <>. Test objects identity with is and is not (compare on id(obj)). Direct composition of comparators is allowed in expressions : x<y<=z>t. Builtin function cmp(o1,o2) �� -1 (o1 < o2), 0 (o1 == o2), 1 (o1 > o2)
Comparison Overriding __lt__(self, other)�� bool1: called for self < other __le__(self, other)�� bool1: called for self <= other __gt__(self, other)�� bool1: called for self > other __ge__(self, other)�� bool1: called for self >= other __eq__(self, other)�� bool1: called for self == other __ne__(self, other)�� bool1: called for self != other
and for self <> other
__cmp__(self,other)�� int: called for self compared to other,
self<other��value<0, self==other��value=0, self>other��value>0
1 Any value usable as boolean value, or a NotImplemented value if
cannot compare with such other type.
Operators as Functions
Operators are also defined as functions in standard operator module.
Comparison lt(a,b) = __lt__(a,b) le(a,b) = __le__(a,b) eq(a,b) = __eq__(a,b) ne(a,b) = __ne__(a,b) ge(a,b) = __ge__(a,b) gt(a,b) = __gt__(a,b) Logical / Boolean not_(o) = __not__(o) truth(o) is_(a,b) is_not(a,b) and_(a,b) = __and__(a,b) or_(a,b) = __or__(a,b) xor(a,b) = __xor__(a,b) Arithmetic abs(o) = __abs__(o) add(a,b) = __add__(a,b) sub(a,b) = __sub__(a,b) mul(a,b) = __mul__(a,b) div(a,b) = __div__(a,b) mod(a,b) = __mod__(a,b) truediv(a,b) = __truediv__(a,b) floordiv(a,b) = __floordiv__(a,b) neg(o) = __neg__(o) pos(o) = __pos__(o) pow(a,b) = __pow__(a,b) Bit Level lshift(a,b) = __lshift__(a,b) rshift(a,b) = __rshift__(a,b) inv(o) = invert(o) = __inv__(o) = __invert__(o) Sequences concat(a,b) = __concat__(a,b) contains(a,b) = __contains__(a,b) countOf(a,b) indexOf(a,b) repeat(a,b) = __repeat__(a,b) setitem(a,b,c) = __setitem__(a,b,c) getitem(a,b) = __getitem__(a,b) delitem(a,b) = __delitem__(a,b) setslice(a,b,c,v) = __setslice__(a,b,c,v) getslice(a,b,c) = __getslice__(a,b,c) delslice(a,b,c) = __delslice__(a,b,c) Type Testing
These functions must be considered as not reliable.
isMappingType(o) isNumberType(o) isSequenceType(o) Attribute and Item Lookup attrgetter(attr) �� fct: where fct(x)��x.attr itemgetter(item) �� fct: where fct(x)��x[item]
False : None, zero numbers, empty containers. False �� 0. True : if not false. True �� 1.
bool(expr) �� True | False
Logical not : not expr Logical and : expr1 and expr2 Logical or : expr1 or expr2
Logical and and or use short path evaluation.
Bool Cast Overriding __nonzero__(self) �� bool: test object itself1
1 If __nonzero__ undefined, look at __len__, else object is true.
Builtin integer types : int (like C long), long (unlimited integer)
int(expr[,base=10]) �� int: cast of expr long(expr[,base=10]) �� long: cast of expr
Builtin floating point types : float (like C double), complex (real and imaginary parts are float).
float(expr) �� float: representation of expr complex(x[,y]) �� complex: number: x+yj
[x+]yj �� complex: number, ex: 3+4j -8.2j
c.real �� float: real part of complex number c.img �� float: imaginary part of complex number c.conjugate() �� complex: conjugate of complex number (real,-img)
Maximum int integer in sys.maxint. Automatic conversions between numeric types. Automatic conversions from int to long when result overflow max int. Direct conversions from/to strings from/to int, long�� via types constructors.
Type Decimal defined in standard module decimal. Base fixed type compact storage arrays in standard module array.
-x +x x+y x-y x*y x/y 1 x//y 1 x%y 2 x**y 2
1 With from __future__ import division, / is true division
(1/2��0.5), and // is floor division (1//2��0). Else for integers / is still floor division.
2 % is remainder operator, ** is power elevation operator (same as
pow). Functions
Some functions in builtins.
abs(x) �� absolute value of x divmod(x,y) �� (x/y,x%y) oct(integer) �� str: octal representation of integer number hex(integer) �� str: hexadecimal representation of integer number
Representation formating functions in strings Formating (p6) and Localization (p7).
Math Functions
Standard floating point functions/data in standard math module.
acos(x) �� float: radians angle for x cosinus value : [-1��1] ��[0����] asin(x) �� float: radians angle for x sinus value : [-1��1] ��[-��/2��+��/2] atan(x) �� float: radians angle for x tangent value : [-�ޡ���] ��]-��/2��
atan2(x,y) �� float: randians angle for x/y tangent value ceil(x) �� float: smallest integral value >= x cos(x) �� float: cosinus value for radians angle x cosh(x) �� float: hyperbolic cosinus value for radians angle x exp(x) �� float: exponential of x = ex fabs(x) �� float: absolute value of x floor(x) �� float: largest integral value <= x fmod(x,y) �� float: modulo = remainder of x/y frexp(x) �� (float,int): (m,y) m mantissa of x, y exponent of x — where
ldepx(x,i) �� float: x multiplied by 2 raised to i power: x * 2i log(x) �� float: neperian logarithm of x
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log10(x) �� float: decimal logarithm of x modf(x) �� (float{2}): (f,i) f signed fractional part of x, i signed integer
part of x
pow(x,y) �� float: x raised to y power (xy) sin(x) �� float: sinus value for radians angle x sinh(x) �� float: hyperbolic sinus value for radians angle x sqrt(x) �� float: square root of x (��x) tan(x) �� float: tangent value for radians angle x tanh(x) �� float: hyperbolic tangent value for radians angle x
pi �� float: value of �� (pi=3.1415926535897931) e �� float: value of neperian logarithms base
Module cmath provides similar functions for complex numbers.
Random Numbers
Randomization functions in standard random module. Module functions use an hidden, shared state, Random type generator (uniform distribution). Functions also available as methods of Random objects.
seed([x]) ➤ initialize random number generator random()�� float: random value in [0.0, 1.0[ randint(a,b)�� int: random value in [a, b] uniform(a, b)�� float: random value in [a, b[ getrandbits(k)�� long: with k random bits randrange([start,]stop[,step])�� int: random value in range(start,
stop, step)
choice(seq)�� value: random item from seq sequence shuffle(x[,rndfct]) ➤ items of x randomly reordered using rndfct() sample(population,k)�� list: k random items from polulation
Alternate random distributions : betavariate(alpha,beta),
expovariate(lambd), gammavariate(alpha,beta), gauss(mu,sigma), lognormvariate(mu, sigma), normalvariate(mu,sigma), vonmisesvariate(mu,kappa), paretovariate(alpha), weibullvariate(alpha,beta).
Alternate random generator WichmannHill class. Direct generator manipulation : getstate(), setstate(state),
In module os, see :
os.urandom(n) �� str: n random bytes suitable for cryptographic use
Other Math Modules
Advanced matrix, algorithms and number crunching in third party modules like numpy (evolution of numarray / Numeric), gmpy (multiprecision arithmetic), DecInt, scipy, pyarray, �� See sites SciPy, BioPython, PyScience,��
Numbers Casts Overriding __int__(self) �� int: called for int(self) __long__(self) �� long: called for long(self) __float__(self) �� float: called for float(self) __complex__(self) �� complex: called for complex(self) __oct__(self) �� str: called for oct(self) __hex__(self) �� str: called for hex(self) __coerce__(self,other) �� value: called for coerce(self,other)
Work with int and long data.
~x �� inverted bits of x x^y �� bitwise exclusive or on x and y x&y �� bitwise and on x and y x|y �� bitwise or on x and y x<<n �� x shifted left by n bits (zeroes inserted) x>>n �� x shifted right by n bits (zeroes inserted) Binary structures manipulations in standard module struct. Advanced binary structures mapping and manipulation in third party modules : ctypes, xstruct, pyconstruct, ��
Bit Level Overriding __and__(self,other) �� value: for self & other __or__(self,other) �� value: for self | other __xor__(self,other) �� value: for self ^ other __lshift__(self,other) �� value: for self << other __rshift__(self,other) �� value: for self >> other __invert__(self) �� value: for ~self __iand__(self,other) ➤ called for self &= other __ior__(self,other) ➤ called for self |= other __ixor__(self,other) ➤ called for self ^= other __ilshift__(self,other) ➤ called for self <<= other __irshift__(self,other) ➤ called for self >>= other
Simple quoted 'Hello' or double-quoted "Hello". Use triple [simple|double] quotes for multi-lines strings :
"""Hello, how are you ?"""
Strings are immutable (once created a string cannot be modified in place). Strings can contain binary data, including null chars (chars of code 0). Strings are sequences, see Indexing (p8) for chars indexation (slicing) and other operations.
chr(code)�� str: string of one char ord(char)�� int: code str(expr)�� str: readable textual representation of expr - if available
`expr` �� str: readable textual representation of expr - if available
repr(expr)�� str: evaluable textual representation of expr - if available Escape sequences
\a - bell \b - backspace \e - escape \f - form feed \n - new line \r - carriage return \t - horizontal tab \v - vertical tab \' - single quote \" - double quote \\ - backslash \ooo - char by octal ooo value \xhh - char by hexadecimal hh value \<newline> - continue string on next line.
And for Unicode strings :
\uxxxx - unicode char by 16 bits hexadecimal xxxx value. \Uxxxxxxxx - unicode char by 32 bits hexadecimal xxxxxxxx value. \N{name} - unicode char by name in the Unicode database.
Keep \ escape chars by prefixing string literals with a r (or R) - for 'raw' strings (note : cannot terminate a raw string with a \).
Unicode strings
Quoted as for str, but with a u (or U) prefix before the string :
u"Voiçi" U"""Une bonne journ��e en perspective."""
Can mix strings prefixs r (or R) and u (or U).
You must define your source file encoding so that Python knows how to convert your source literal strings into internal unicode strings.
unichr(code) �� unicode: string of one char ord(unicode char) �� int: unicode code unicode(object[,encoding[,errors]]) �� unicode: unicode
sys.maxunicode �� int: maximum unicode code=fct(compile time
Unicode Chars Informations
Module unicodedata contains informations about Unicode chars properties, names.
lookup(name) �� unicode: unicode char from its name name(unichr[,default]) �� str: unicode name - may raise ValueError decimal(unichr[,default]) �� int: decimal value - may raise ValueError digit(unichr[,default]) �� int: digit value - may raise ValueError numeric(unichr[,default]) �� float: numeric value - may raise
category(unichr) �� str: general unicode category of char bidirectional(unichr) �� str: bidir category of char, may be empty
combining(unichr) �� str/0: canonical combining class of char as integer east_asian_width(unichr) �� str: east asian width mirrored(unichr) �� int: mirrored property in bidi text, 1 if mirrored else
decomposition(unichr) �� str: decomposition mapping, may be empty
normalize(form, unistr) �� str: normal form of string - form in 'NFC',
unidata_version �� str: version of Unicode database used
Methods and Functions
From builtins (see also oct and hex functions for integers to strings) :
len(s) �� int: number of chars in the string
Most string methods are also available as functions in the standard
string module.
s.capitalize() �� string with first char capitalized1 s.center(width[,fillchar]) �� string centered s.count(sub[,start[,end]]) �� int: count sub occurences s.decode([encoding[,errors]]) �� unicode: text decoded - see encodings (p13) s.encode([encoding[,errors]]) �� str: text encoded - see encodings (p13) s.endswith(suffix[,start[,end]]) �� bool: test text ending s.expandtabs([tabsize]) �� string with tabs replaced by spaces s.find(sub[,start[,end]]) �� int/-1: offset of sub s.index(sub[,start[,end]]) �� int: offset of sub - may raise ValueError s.isalnum() �� bool: non empty string with all alphanumeric chars1 s.isalpha() �� bool: non empty string with all alphabetic chars1 s.isdigit() �� bool: non empty string with all digit chars1 s.islower() �� bool: non empty string with all lower chars1 s.isspace() �� bool: non empty string with all space chars1 s.istitle() �� bool: non empty string with titlecase words1 s.isupper() �� bool: non empty string with all upper chars1 s.join(seq) �� string: seq[0]+s+seq[1]+s+��+seq[n-1] s.ljust(width[,fillchar]) �� text string left aligned2 s.lower() �� text string lowered1 s.lstrip([chars]) �� string text with leading chars2 removed s.replace(old,new[,count]) �� string with count firsts old replaced by new s.rfind(sub[,start[,end]]) �� int/-1: last offset of sub s.rindex(sub[,start[end]])�� int: last offset of sub - may raise
s.rjust(width[,fillchar]) �� string text right aligned2 s.rsplit([sep[,maxsplit]])�� [string]: rightmost words delim. by sep2 s.rstrip([chars]) �� string with trailing chars2 removed s.split([sep[,maxsplit]]) �� [string]: words delimited by sep2 s.splitlines([keepends]) �� [string]: list of text lines s.startswith(suffix[,start[,end]]) �� bool: test text begining s.strip([chars]) �� string text with leading+trailing chars2 removed s.swapcase() �� string with case switched1 s.title() �� string with words capitalized1 s.translate(table[,deletechars]) �� string: cleaned, converted3 s.upper() �� string uppered1 s.zfill(witdh) �� string: string prefixed with zeroes to match width
1 Locale dependant for 8 bits strings. 2 Default chars/separator/fillchar is space. 3 For str table must be a string of 256 chars - see
string.maketrans(). For Unicode no deletechars, and table must
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be a map of unicode ordinals to unicode ordinals.
Use % operator between format string and arguments : string%args Formating string contains %[(name)][flag][width][.precision]code If not use %(name)�� �� args = single value or tuple of values. If use %(name)�� �� args = mapping with name as keys.
For mapping, args can be an object with __getitem__ method - see Overriding Mapping Operations (p8).
Format char codes
d signed int. decimal : -324 i signed int. decimal : -324 o unsigned octal : 774 u unsigned decimal 6953 x unsigned hexa : f3a X unsigned hexa : F3A e float. point exp. : -3.256e-12 E float. point exp. : -3.256E-12 f float. point dec. : -0.0000032 F float. point dec. : -0.0000032 g like e or f G like E or F c character (1 char str or code) % %% �� % r object format like repr(object) s object format like str(object)
With string.Template objects. Use common $ syntax : $$ ➤ single $ ; $name or ${name} ➤ value for name. tmpl = string.Template(template_string) tmpl.substitute(mapping[,**kwargs]) �� string: template filled tmpl.safe_substitute(mapping[,**kwargs]) �� string: template filled tmpl.template �� string
Can subclass Template to build your own templating (see doc, sources).
See also modules formatter.
Module textwrap has a TextWrapper class and tool functions. tw = textwrap.TextWrapper([��]) �� new text wrapper using named params as corresponding attributes values
tw.width �� int: max length of wrapped lines (default 70) tw.expand_tabs �� bool: replace tabs by text.expandtabs() (default
tw.replace_whitespace �� bool: replace each whitespace by space
(default True)
tw.initial_indent �� string: prepend to first wrapped line (default '') tw.subsequent_indent �� string: prepend to other wrapped lines
(default '')
tw.fix_sentence_endings �� bool: try to separate sentences by two
spaces (default False)
tw.break_long_words �� bool: break words longer than width (default
tw.initial_indent �� string: prepend to first wrapped line (default '') tw.wrap(text) �� [string]: list of text lines, each with max width length -
no final newline
tw.fill(text) �� string: whole text, lines wrapped using newlines
Two convenient functions use temporary TextWrapper, built using named parameters corresponding to attributes.
wrap(text[,width=70[,��]]) �� [string] fill(text[,width=70[,��]]) �� string dedent(text) �� string: remove uniform whitespaces at beginning of text
Standard module string provide several constants (do not modify, they are used in string manipulation functions) and some str functions are not available as methods.
ascii_letters �� str: lowercase and uppercase chars ascii_lowercase �� str: lowercase a-z chars ascii_uppercase �� str: uppercase A-Z chars digits �� str: 0-9 decimal digit chars hexdigits �� str: 0-9a-fA-F hexadecimal digit chars letters �� str: lowercase and uppercase chars1 lowercase �� str: lowercase a-z chars1 octdigits �� str: 0-7 octal digit chars punctuation �� str: ascii chars considered as punctuation in C locale printable �� str: printable chars uppercase �� str: uppercase A-Z chars1 whitespace �� str: whitespace chars (spc, tab, cr, lf, ff, vt)
capwords(s) �� str: split �� capitalize �� join maketrans(from,to) �� translation table usable in str.translate - from and
to must have same length
Definition is locale dependant.
Regular Expressions
Standard module re has a powerfull regexp engine. See regexp HOWTO at http://www.amk.ca/python/howto/regex/. Use raw string r"��" notation.
See also external projects pyparsing, PLY (Python Lex-Yacc), tpg (Toy Parser Generator)��
Metacharacters : . ^ $ * + ? { } [ ] \ | ( ), may use \ escape.
. ➤ match any character except a newline (including newline with DOTALL
^ ➤ match start of string (and start of lines with MULTILINE option) $ ➤ match end of string (and end of lines with MULTILINE option)
expr* ➤ match 0 or more repetitions of expr (as much as possible) expr+ ➤ match 1 or more repetitions of expr (as much as possible) expr? ➤ match 0 or 1 expr expr*? ➤ match like expr* but as few as possible expr+? ➤ match like expr+ but as few as possible expr?? ➤ match like expr? but as few as possible expr{m} ➤ match m repetitions of expr expr{[m],[n]} ➤ match from m to n repetitions of expr, missing m default to 0 and missing n default to infinite expr{[m],[n]}? ➤ match like expr{[m],[n]} but as few as possible
[set] ➤ match one char in the set defined by : ^ �� at begining, invert set definition
x-y �� chars from x to y
\x �� see Escape sequences for strings (p5) \- , \] �� chars - and ] (- and ] at the beginning match - and ]
x �� char x (including other re metacharacters)
exprA|exprB ➤ match exprA or exprB, short path evaluation
(expr) ➤ match expr and build a numbered group (?[i][L][m][s][u][x]) ➤ (at least one ot iLmsux char) group match empty
string, modify options flags for entire expression - see I L M S U X options
(?:expr) ➤ match expr but dont build a group (?P<name>expr) ➤ match expr and build a group numbered and named
(name must be valid Python identifier)
(?P=name) ➤ match text matched by earlier group named name (?#text) ➤ no match, text is just a comment (?=expr) ➤ match if match expr but don't consume input (?!expr) ➤ match if doesn't match expr but don't consume input (?<=expr) ➤ match if current position is immediatly preceded by a match
for fixed length pattern expr
(?<!expr) ➤ match if current position is immediatly not preceded by a
match for fixed length pattern expr
(?(num/name)yesexpr[|noexpr]) ➤ try to match yesexpr if group
num/name exists, else try to match noexpr
Escape Sequences
\n \nn ➤ match3 group number n (nn) where first n��0 \ooo \0o ➤ match3 char with octal value ooo (0o) \A ➤ match only at the start of the string \b ➤ match3 empty string at beginning or end of a word1+2 \B ➤ match empty string not at beginning or end of a word1+2 \d ➤ match char class decimal digit [0-9] \D ➤ match char class non-digit [^0-9] \s ➤ match char class whitespace [ \t\n\r\f\v] \S ➤ match char class non-whitespace [^ \t\n\r\f\v] \w ➤ match char class alphanumeric [a-zA-Z0-9_] \W ➤ match char class non-alphanumeric [^a-zA-Z0-9_] \Z ➤ match end of string \a \b \f \n \r \t \v \x \\ ➤ same as string escapes \c ➤ for other c chars, match char c
1 Depends on UNICODE flag. 2 Depends on LOCALE flag. 3 When out of char class definition ([��])
Flag Options
IGNORECASE (I) : case insensitive expression - not locale dependant. LOCALE (L) : make \w \W \b \B locale dependant. MULTILINE (M) : ^ and $ match begining/end of string and lines. Else
^ and $ match only beginning and end of string.
DOTALL (S) : make . match any char including newline. Else newline
UNICODE (U) : make \w \W \b \B unicode dependant. VERBOSE (X) : ignore whitespaces and make # starting comments
(except when space and # are escaped or in char class).
Matching and Searching
Can use re functions, or compile expressions into SRE_Pattern objects and use their methods. See Flag Options supra for flags parameters.
search(pattern,string[,flags])�� MatchObject/None: scan throught
string to find substrings matching pattern
match(pattern,string[,flags])�� MatchObject/None: try to match string
with pattern
split(pattern,string[,maxsplit=0])�� [string]: split string by occurences
of pattern - if maxsplit specified, remainder is put in last item of list
findall(pattern,string[,flags])�� [string]/[(string)]: find non-
overlapping substrings matching pattern - eventually empty matchs - return list of tuples if pattern has groups
finditer(pattern,string[,flags])�� iterator over [MatchObject] - same
as findall but with an iterator
sub(pattern,repl,string[,count=0])�� string: replace substrings matching
pattern by repl - repl as string can contain back references1 to identified substring - repl as fct(MatchObject) return replacement string - pattern may be RE_Pattern object
subn(pattern,repl,string[,count=0])�� (string,int): same as sub, 2nd
item is count of substitutions
escape(string)�� string: non-alphanumerics backslashed
If you need to reuse a pattern, compile it one time for all. pat = re.compile(pattern[,flags])�� RE_Pattern object pat.match(string[,pos[,endpos]]) �� same as match function2 pat.search(string[,pos[,endpos]]) �� same as search function2 pat.split(string[,maxsplit=0])�� same as split function2 pat.findall(string[,pos[,endpos]])�� same as findall function2 pat.finditer(string[,pos[,endpos]])�� same as finditer function2 pat.sub(repl,string[,count=0])�� same as sub function pat.subn(pattern,repl,string[,count=0])�� same as subn function pat.flags �� int: flags used at compile time pat.pattern �� string: pattern used at compile time pat.groupindex �� dict: mapping of group names to group numbers Several functions/methods return MatchObject objects. m.expand(template)�� string: do backslash substitution on template (like
sub method) using match object groups values
m.group([group[,��]])�� string/(string): subgroups of the match from numbers or names m.groups([default=None])�� (string): all subgroups of the match - default give access to subgroups not in the match m.groupdict([default=None])�� dict: name��subgroup: all named 6a 6b 6c

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subgroups of the match - default give access to subgroups not in the match m.start([group=0])�� int: index of start of substring matched by group,
-1 if group exists but not in match
m.end([group=0])�� int: index of end of substring matched by group, -1 if group exists but not in match m.span([group=0])�� (int{2}): values of start and end methods for the group m.pos �� int: pos value of search/match method m.endpos �� int: endpos value of search/match method m.lastindex �� int/None: index of last matched capturing group m.lastgroup �� string/None: name of last matched capturng group m.re �� RE_Pattern: pattern used to produce match object m.string �� string: string used in match/search to produce match object
1 Back references extended to \g<groupnum> and \g<groupname>. 1 Using part of string between pos and endpos.
Group number 0 correspond to entire matching.
Standard module locale provide posix locale service (internationa- lization).
setlocale(category[,locale]) �� current/new settings: if locale specified
(as string or as tuple(language code, encoding)) then modify locale settings for category and return new one - if locale not specified or None, return current locale - not thread safe
localeconv()�� dict: database of local conventions nl_langinfo(option)�� string: locale-specific informations - not available
on all systems - options may vary on systems - see options p7
getdefaultlocale([envvars])��(language code, encoding): try to
determine default locale settings
getlocale([category])�� current LC_* setting for category - category
default to LC_CTYPE - for language code and ancoding it may be None
getpreferredencoding([do_setlocale])�� str: user preffered encoding
for text data - set do_setlocale to False to avoid possible call to
setlocale() normalize(localename)�� normalized locale code for localename - usable
with setlocale() - return localename if normalization fails
resetlocale([category]) ➤ reset locale for category to default setting -
category default to LC_ALL
strcoll(s1,s2)�� int: compare two strings - follow LC_COLLATE setting
- return 0 if s1==s2, <0 if s1<s2, >0 if s1>s2
strxfrm(string)�� string:transform string for locale-aware comparison format(format,val[,grouping])�� string:convert val float using format (%
operator conventions) - follow LC_NUMERIC settings (decimal point, + grouping if it is true)
str(float)�� string: convert float - follow LC_NUMERIC settings (decimal
atof(string)�� float: convert string to float - follow LC_NUMERIC settings atoi(string)�� int: convert string to integer - follow LC_NUMERIC settings
CHAR_MAX �� symbolic constant used by localeconv()
LC_CTYPE �� character type - case change behaviour LC_COLLATE �� strings sorting - strcoll() and strxfrm() functions LC_TIME �� time formating - time.strftime() LC_MONETARY �� monetary values formating - options from localeconv() LC_MESSAGES �� messages display - os.strerror() - not for Python
LC_NUMERIC �� numbers formatting - format(), atoi(), atof() and
str() of this module (dont modify normal Python number formating)
LC_ALL �� all locales - used to change/retrieve the locale for all categories
nl_langinfo options
key nl_langinfo() value usage
name of character encoding
usable as format for strftime() for time and date
key nl_langinfo() value usage
usable as format for strftime() for date
usable as format for strftime() for time
usable as format for strftime() for time in am/pm format
name of the nth day of the week - first day is sunday
abbreviated name of the nth day of the week - first day is sunday
MON_1�� MON_12 name of the nth month ABMON_1�� ABMON_12
abbreviated name of the nth month
radix character (decimal dot/comma/��)
separator character for thousands
regular expression (of C library!) usable for yes reply
regular expression (of C library!) usable for no reply
currency symbol, preceded by - if should appear before the value, by + if should appear after the value, by . if should replace radix character
era - generally not defined - same as E format in
year in era
usable as format for strftime() for date and time with era
usable as format for strftime() for date with era
up to 100 values representing 0 to 99
localeconv keys
key meaning
Local currency symbol for monetary values.
Decimal point character for numbers.
Number of fractional digits used in local formatting of monetary values.
[int]: relative positions of 'thousands_sep' in numbers. CHAR_MAX at the end stop grouping. 0 at the end repeat last group.
International currency symbol of monetary values.
Number of fractional digits used in international formatting of monetary values.
mon_decimal_point Decimal point used for monetary values. mon_grouping
Equivalent to 'grouping', used for monetary values.
mon_thousands_sep Group separator used for monetary values. n_cs_precedes
True if currency symbol preceed negative monetary values, false if it follow.
True if there is a space between currency symbol and negative monetary value.
Position of negative sign for monetary values1.
Symbol used to annotate a negative monetary value.
True if currency symbol preceed positive monetary values, false if it follow.
True if there is a space between currency symbol and positive monetary value.
Position of positive sign for monetary values1.
Symbol used to annotate a positive monetary value.
Character used between groups of digits in
key meaning
1 Possible values : 0=currency and value surrounded by
parentheses, 1=sign should precede value and currency symbol,
2=sign should follow value and currency symbol, 3=sign should
immediately precede value, 4=sign should immediately follow value, LC_MAX=nothing specified in this locale.
Multilingual Support
Standard module gettext for internationalization (I18N) and localization (L10N) services - based on GNU gettext API + higher interface. See docs for explanations about tools usage.
Base API bindtextdomain(domain[,localedir])�� str: bounded directory - bind
domain to localedir directory if specified (used when searching for .mo files)
bind_textdomain_codeset(domain[,codeset])�� codeset binding: bind
domain to codeset if specified - change xxgettext() returned strings encoding
textdomain([domain])�� global domain: set global domain if specified
and not None
gettext(message)�� string: localized translation of message - based on
current global domain, language, and locale directory - usually aliased as _ in local namespace
lgettext(message)�� string: like gettext(), using preferred encoding dgettext(domain,message)�� string: like gettext(), looking in
specified domain.
ldgettext(domain,message)�� string: like dgettext(), using preferred
ngettext(singular,plural,n)�� string: like gettext(), but consider plural
forms (see Python and GNU gettext docs)
lngettext(singular,plural,n)�� string: like ngettext(), using preferred
dngettext(domain,singular,plural,n)�� string: like ngettext(), looking
in specified domain.
ldngettext(domain,singular,plural,n)�� string: like dngettext(),
using preferred encoding
Generally _ is bound to gettext.gettext, and translatable strings are written in sources using _('thestring'). See docs for usage examples.
Class based API
The recommended way. Module gettext defines a class
Translations, dealing with .mo translation files and supporting str/unicode strings.
find(domain[,localedir[,languages[,all]]])�� str/None: .mo file name
for translations (search in localedir/language/LC_MESSAGES/domain.mo)
]]]])��Translations: object from class class_ (default to
GNUTranslations, constructor take file object as parameter) - if true
fallback allow to return a NullTranslations if no .mo file is found, default to false (raise IOError) - codeset change charset used to encode translated strings
install(domain[,localedir[,unicode[,codeset]]]) ➤ install _ function in
Python's builtin namespace, to use _('thestring')
Null Translations
The NullTranslations is a base class for all Translations.
t.__init__([fp]) ➤ initialize translations: fp is a file object - call
_parse(fp) if it is not None
t._parse(fp) ➤ nothing: subclasses override to read data from the file t.add_fallback(fallback) ➤ add fallback used if cannot found
translation for a message Define methods gettext, lgettext, ngettext, lngettext as in the base API. And define speciale methods ugettext and ungettext returning unicode strings (other forms return encoded str strings). 7a 7b 7c

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Return translated message, forwarding to fallback if it is defined. Overriden in subclasses.
t.info()�� return protected _info attribute t.charset()�� return protected _charset attribute t.output_charset()�� return protected _output_charset attribute
(defining encoding used to return translated messages)
t.set_output_charset(charset) ➤ set _output_charset attribute t.install([unicode]) ➤ bind _ in builtin namespace to self.gettext() or self.ugettext() upon unicode (default to false)
GNU Translations
The GNUTranslations class (subclass of NullTranslations) is based on GNU gettext and .mo files. Messages ids and texts are coerced to unicode. Protected _info attribute contains message translations. Translation for empty string return meta-data (see doc). Define methods gettext, lgettext, ugettext, ngettext,
lngettext, ungettext as in NullTranslations interface - same
rules for return values (str/unicode). Message translations are searched in catalog, then in fallback if defined, and if no translation is found, message itself is returned (for n�� methods, return singular forms if n=1 else plural forms).
Basic containers kind : -sequences (ordered collections) : list, tuple,str, any iterable,�� -mappings (unordered key/value) : dict�� -sets (unordered collections) : set, frozenset��
Operations on Containers
For strings, items are chars. For mappings, items are keys. item in container �� bool: test item �� container1 item not in container �� bool: test item container1
for var in container: �� ➤ iterate var over items of container
len(container) �� int: count number of items in container2 max(container) �� value: biggest item in container min(container) �� value: smallest item in container sum(container) �� value: sum of items (items must be number-compatible)
1 For strings test if expr is a substring of sequence. 2 Container must provide direct length method - no generator.
Copying Containers
Default containers constructors build new container with references to existing objects (shallow copy). To duplicate content too, use standard module copy. See Copying Objects (p3).
Overriding Containers Operations __len__(self)�� int: called for len(self) __contains__(self,item)�� bool: called for item [not] in self
You can override iterable protocol on containers too.
Sequences are ordered collections : str, unicode, list, tuple,
buffer, xrange, array.array�� any user class defining sequences
interface, or any iterable data.
Lists & Tuples
Builtin types list and tuple store sequences of any objects. Lists are mutable, tuples are immutable. Declare a list : [item[,��]] Declare a tuple : (item[,��]) Notes : [] ➤ empty list ;() ➤ empty tuple ; (item,) ➤ one item tuple.
list(object) �� list: new list (cast from object / duplicate existing) tuple(object) �� tuple: new tuple (cast from object / duplicate existing) range([start,]stop[,step])�� [int]: list, arithmetic progression of
xrange1([start,]stop[,step]) �� xrange: object generating arithmetic
progression of integers
Unless using a sequence as a mapping key, or ensuring it is immutable data, prefer list to tuple.
1 Use in place of range to avoid building huge lists just for indexing.
Operations on Sequences
See Operations on Containers (p8) too. seq1 + seq2 �� concatenation of seq1 and seq2 sequence * n �� concatenation of sequence duplicated n times n * sequence �� concatenation of sequence duplicated n times
reversed(sequence)�� iterator throught sequence in reverse order sorted(sequence[,cmp[,key[,reverse]]])�� list: new list, sorted items
from iterable - see list.sorted()
filter1(fct,sequence)�� list: new list where fct(item) is True. Use None
fct for a boolean test on items
map1(fct,sequence,��)�� list: new list where ith item is fct(ith items of
reduce(fct,sequence[,initializer])�� value: fct applied cumulatively to
sequence items, f(f(��f(f(f(initializer,a),b),c,��)
zip1(sequence,��)�� list: list of tuples, ith tuple contains ith items of each
1 See Iteration Tools (p9) as replacement (avoid creating a new
Use index [i] and slice [i:j[:step]] syntax. Indexs zero-based. Negative indexs indexing from end. Default step is 1, can use negative steps. Sub-sequences indexs between items. l = [e1,e2,e3,��,en-2,en-1,en] l[0]�� e1 l[1]�� e2 l[-2]�� en-1 l[-1]�� en l[0:n]��[e1,e2,e3,��,en-2,en-1,en] l[:]��[e1,e2,e3,��,en-2,en-1,en] l[i:]��[ei+1,ei+2,ei+3,��,en-1,en] l[:i]��[e1,e2,��,ei-2,ei-1,ei] items indexs -n -n+1 -n+2 �� -2 -1 0 1 2 �� n-2 n-1 e1 e2 e3 ��item�� en-1 en 0 1 2 3 �� n-2 n-1 n -n -n+1 -n+2 -n+3 �� -2 -1 slicing indexs
Slice objects
Defines index range objects, usable in [] notation.
slice([start,]stop[,step])�� slice object
slice.indices(len)�� (int{3}): (start,stop,stride) Ordered sets of data indexed from 0. Members start, stop, step.
Extended Slicing
Multiple slices notation - corresponding to a selection in a multi- dimension data - can be written using notation like [ a , x:y:z , : , : , : , m:n ]. Ellipsis notation can be used to fill multiple missing slices, like [ a , x:y:z , ... , m:n ]. See docs.
Three dot notation ... is replaced internally by Ellipsis object.
Operations on mutable sequences
Mutable sequences (ex. list) can be modified in place. Can use mutable sequence indexing in left part of assignment to modify its items : seq[index]=expr ; seq[start:stop]=expr ; seq[start:stop:step]=expr seq.append(item) ➤ add item at end of sequence seq.extend(otherseq) ➤ concatenate otherseq at end of sequence seq.count(expr) �� int: number of expr items in sequence seq.index(expr[,start[,stop]])�� int: first index of expr item seq.insert(index,item) ➤ item inserted at index seq.remove(expr) ➤ remove first expr item from sequence seq.pop([index]) �� item: remove and return item at index (default -1) seq.reverse() ➤ items reversed in place seq.sort([cmp][,key][,reverse]) ➤ items sorted in place - cmp : custom comparison fct(a,b), retval <0 or = 0 or >0 - key : name of items attribute to compare - reverse : bool
del seq[index] ➤ remove item from sequence del seq[start:stop[:step]] ➤ remove items from sequence
Overriding Sequences Operations __getitem__(self,index2)�� value: item at index, called for
__setitem__1(self,index2,value) ➤ set item at index to value, called
for self[index]=value
__delitem__1(self,index2) ➤ remove item at index, called for
del self[index]
1 Only for mutable sequences. 2 Parameter index can be a slice [start,stop,step] - replace old
__getslice__, __setslice__, __delslice__. Can also override arithmetic operations __add__ (concatenation ) and __mul__ (repetition ), container operations and object operations.
Builtin type dict. Store key:value pairs. Declare a dictionary : { key :value [,��]} {}
dict()�� dict: empty dictionary (like {}) dict(**kwargs)�� dict: from named parameters and their values dict(iterable)�� dict: from (key,value) by iterable dict(otherdict)�� dict: duplicated fro another one (first level) Operations on Mappings
See Operations on Containers (p8) too, considering operations on keys. d[key]�� value for key1 d[key]=value ➤ set d[key] to value
del d[key] ➤ removes d[key] from d1
d.fromkeys(iterable[,value=None]) �� dict: with keys from iterable and all same value d.clear() ➤ removes all items from d d.copy() �� dict: hallow copy of d d.has_key(k)�� bool: test key presence - same as k in d d.items()�� list: copy of d's list of (key, item) pairs d.keys()�� list: copy of d's list of keys d.update(otherd) ➤ copy otherd pairs into d d.update(iterable) ➤ copy (key,value) pairs into d d.update(**kwargs) ➤ copy name=value pairs into d d.values()�� list: copy of d's list of values d.get(key,defval)�� value: d[key] if key��d, else defval d.setdefault(key[,defval=None]) �� value: if keyd set d[key]=defval, return d[key] d.iteritems()�� iterator over (key, value) pairs d.iterkeys()�� iterator over keys d.itervalues()�� iterator over values d.pop(key[,defval]) �� value: del key and returns the corresponding value. If key is not found, defval is returned if given, otherwise KeyError is raised d.popitem() �� removes and returns an arbitrary (key, value) pair from d
1 If key doesn't exist, raise KeyError exception.
Overriding Mapping Operations __getitem__(self,key)�� value for key, called for self[key] __setitem__(self,key,value) ➤ set value for key, called for
__delitem__(self,key,value) ➤ remove value for key, called for
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del self[key]
Can also override container operations and object operations.
Other Mappings
For on-disk mappings, see standard module shelve, and database modules . For ordered mappings see third party modules OrderedDict.
Unordered collections of unique items. Frozen sets are immutable once created.
set([iterable]) �� set: using values from iterable frozenset([iterable]) �� frozenset: using values from iterable Operations on Sets
See Operations on Containers (p8) too. s.issubset(others)�� bool: test s others s.issuperset(others)�� bool: test others s s.add(item) ➤ add item to set s.remove(item) ➤ remove item from set1 s.clear() ➤ emoves all items from (not forzen) set s.intersection(others)�� set: s �� others s & others �� set: s �� others s.union(others) �� set: s �� others s | others �� set: s �� others s.difference(others) �� set: [x / x��s and x∉others] s - others �� set: [x / x��s and x∉others] s.symmetric_difference(others)�� set: [x / x��s xor x��others] s ^ others �� set: [x / x��s xor x��others] s.copy()�� set: shallow copy of s s.update(iterable) ➤ adds all values from iterable to s
1 Raise KeyError if object not in set.
Results set have same type as s object (set/frozenset).
Generally containers follow Python idioms, you can use : len(cont), cont[i], for item in cont:��
Standard module array provides efficient array of basic types. It uses compact storage for elements of same type.
Type Codes
n tc C type py type n tc C py type
1 'b' signed char
'B' unsigned char int
1 'c' char
'u' unicode char
2 'h' signed short int 2
'H' unsigned short int
2 'i' signed int
'I' unsigned int
4 'l' signed long
'L' unsigned long long
4 'f' float
'd' double
n=size in bytes, tc=char typecode to use
Functions array(tc,[iterable]) �� array: with typecode tc, initialized from iterable
a.typecode �� str: typecode of a data a.itemsize �� int: bytes size of a data a.append(expr) ➤ append item expr to end of a a.extend(array) ➤ append items from another array a.count(expr) �� int: number of expr items a.index(expr) �� int: first index of expr item a.insert(index,expr) expr item inserted at index a.remove(expr) ➤ remove first expr item a.pop([index]) �� value: return and remove item at index (default -1) a.reverse() ➤ items in array are reversed a.buffer_info() �� (int{2}): current storage infos (address,items count) a.byteswap() ➤ swap bytes of array items a.fromfile(f,n) ➤ append n items read from real binary file f1 a.tofile(f) ➤ write all items to real binary file f a.fromlist(list) ➤ extend array from values in list a.tolist() �� list: items in a list a.fromstring(s) ➤ extend array from values in binary buffer s (string) a.tostring() �� str: items in binary representation a.fromunicode(s) ➤ extend 'u' array from data in unicode stirng a.tounicode() �� unicode: convert 'u' array to unicode string
1 If less items than needed, get available ones then raise
Old methods read and write replaced by fromfile and tofile.
Standard module collections provides queues management.
deque([iterable])�� deque: initialized from iterable
q.append(x) ➤ add x to right side of deque q.appendleft(x) ➤ add x to left side of deque q.clear() ➤ remove all elements from deque q.extend(iterable) ➤ extend right side of deque with iterable items q.extendleft(iterable) ➤ extend left side of the deque with iterable items q.pop() �� item: pop and return item from dequeue right side q.popleft() �� item: pop and return item from dequeue left side q.rotate(n) ➤ rotate deque from n steps, to right if n>0, to left if n<0 Can also use standard operations on sequences : len(q),
reversed(q), copy.copy(q), copy.deepcopy(q), item in q, q[-1],
and serialization via pickling protocol.
Priority Queues
Standard module heapq. Structure a list as a priority queue.
heapify(x) ➤ transform list x into heap heappush(heap,item) ➤ push item onto heap heappop(heap)�� item: pop and return smallest item from the heap heapreplace(heap,newitem)�� item: pop and return smallest item from
the heap, push newitem
nlargest(n,iterable)�� list: n largest from iterable nsmallest(n,iterable)�� list: n smallest items from iterable Sorted List
Standard module bisect maintains lists sorted (via basic bisection algo).
bisect_left(list,item[,lo[,hi]])�� int: index to insert item at leftmost
sorted position1
bisect_right(list,item[,lo[,hi]])�� int: index to insert item at
rightmost sorted position1
bisect(��) ➤ alias for bisect_right(��) insort_left(list,item[,lo[,hi]]) ➤ insert item at leftmost sorted
insort_right(list,item[,lo[,hi]]) ➤ insert item at rightmost sorted
insort(��) ➤ alias for insort_right(��)
1 With list previously sorted.
Iteration Tools
Standard module itertools provides some practical iterators.
chain(iterable[,��])�� iterator over items of several iterables count([start])�� iterator over integers from start (default 0) cycle(iterable)�� iterator cycling over iterable items dropwhile(predicatefct,iterable)�� iterator over items of iterable where
predicatefct(item) is false
groupby(iterable[,keyfct])�� iterator over (key value,group1 of items
where keyfct(item)=key value), default keyfct is identity
ifilter(predicate,iterable)�� iterator over items of iterable where
predicatefct(item) is true - None predicate filter items being true
ifilterfalse(predicate,iterable)�� iterator over items of iterable where
predicatefct(item) is false - None predicate filter items being false
imap(function,iterable[,��])�� iterator over function(items at same index
from iterables2), None function return tuples items
islice(iterable,[start,]stop[,step])�� iterator over items at slice3 indexs
from iterable, None stop goes up to end
izip(iterable[,��])�� iterator over tuple(items at same index from
repeat(object[,count])�� iterator returning object over and over again, up
to count times (default to infinite)
starmap(function,iterable)�� iterator over function(*tuple item from
takewhile(predicatefct,iterable)�� iterator over items of iterable where
predicatefct(item) is true
tee(iterable[,n]) �� n independent iterators from same iterable4, default
1 Group of items is internally used - must save it as list if needed
after current iteration.
2 Stop at end of shorter iterable. 3 Slice parameters cannot be negative. 4 Don't use iterable out of tee created iterators.
Module time
Standard module time defines common functions and data.
Date & Time Data
• float_time = float containing seconds from 'epoch' (january 1 1970 on Unix - see gmtime(0)), with sub-second precision in decimal part. • tuple_time = tuple containing 9 int (see table). struct_time = tuple/object with int attributes (see table).
# attribute value # attribute value 0 tm_year
1 tm_mon
0��6 (monday=0)
2 tm_mday
3 tm_hour
4 tm_min
0 (no)
1 (yes)
-1 (unknown)
• float_delay = float containing seconds, with sub-second precision. DST is local time, UTC is universal (GMT) time.
accept2dyear �� [rw] bool: accept two-digit year values (default true),
modifiable via environment var PYTHONY2K
altzone �� int: offset (pos/neg) in seconds of DST relatively to UTC, in
seconds, use only if daylight is true
daylight �� int: ��0 if a DST timezone is defined timezone �� int: offset (pos/neg) in seconds of local (non DST) timezone tzname �� (str{2}): names of local timezone (non-DST, DST)
Functions asctime([t=2])�� str: build local time string from t (tuple_time or
clock()�� float: processor time in seconds, for accurate relative time
ctime([secs=2])�� str: build local time string from float_time second gmtime([secs=2])�� struct_time: convert float_time to UTC struct_time localtime([secs=2])�� struct_time: convert float_time to DST
mktime(t)�� float_time: convert DST t (tuple_time or struct_time) to
float_time - may raise OverflowError or ValueError
sleep(secs) ➤ execution suspended during secs (float_delay) times,
maybe less (signal catching), may be more (process/threads scheduling)
strftime(format[,t=2]) �� str: build time string from t (tuple_time or
struct_time) using format string (table infra) - may raise ValueError
strptime(string[,format]) �� struct_time: parse string using time
format1 - may raise ValueError
time() �� float_time: current UTC time tzset() ➤ resets time conversion rules accordingly to environnment
variable TZ - unix only, see docs 9a 9b 9c

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1 Default format "%a %b %d %H:%M:%S %Y". Missing values
default to (1900, 1, 1, 0, 0, 0, 0, 1, -1)
2 Param secs default to current time, param t default to local
current time.
Time format strings
Abbreviated weekday name1.
Full weekday name1.
Abbreviated month name1.
Full month name1.
Appropriate date and time representation1.
Month day [01,31].
Hour [00,23].
Hour [01,12].
Year day [001,366].
Month [01,12].
Minute [00,59].
AM or PM1.
Second [00,61].
Year week [00,53] (Sunday based).
Week day [0,6] (0=Sunday).
Year week [00,53] (Monday based).
Appropriate date representation1.
Appropriate time representation1.
Year [00,99].
Year (with century).
Time zone name (no characters if no time zone exists).
Literal % char.
1 Locale language representation.
Module datetime
Standard module datetime has tools for date/time arithmetics, data extraction and manipulation. Defines class : timedelta, time, date, datetime, [tzinfo].
Module timeit
Standard module timeit has functions to measure processing time of code. It can be used in scripts (see docs), or directly in command line : python -mtimeit [-n N] [-r N] [-s S] [-t] [-c] [-h] [statement [��]] -n N / --number=N execute statement N times -r N / --repeat=N repeat timer N times (default 3) -s S / --setup=S executed S once initially (default pass) -t / --time use time.time() (default except Windows) -c / --clock use time.clock() (default on Windows) -v / --verbose print raw timing results - may repeat option -h / --help print help and exit
Other Modules
Standard module calendar has functions to build calendars. See also third party module mxDateTime.
Normal file operations use Python file objects (or file-like objects with same interface). Some functions directly manipulate files path names (strings). Functions mapping low level OS handlers (mainly those in standard os module) use numeric file descriptors (fd also known as fileno). Raw data use str type (can contain any data byte values, including 0).
File Objects
Standard file type is builtin file. It defines the Python file protocol. Create a file : file(filename[,mode='r'[,bufsize]]) �� file object Mode flags (combinable) : 'r' read, 'w' write new, 'a' write append, '+' update, 'b' binary1, 'U' universal newline2. Buffer size : 0 unbuffered, 1 line buffered, >1 around that size.
Open() is an alias for file()
1 Default text mode tries to interpret newline sequences in the file. 2 Automatically choose newline sequence in CR or LF or CR+LF
adapted from file/to platform.
Methods and Functions
f.close() ➤ file flushed and no longer usable f.fileno() �� int: low level file descriptor (fd) f.flush() ➤ buffers written to file on disk f.isatty() �� bool: indicator file is a terminal f.read([size]) �� str: block of data read from file f.readline() �� str: next line read from file, end of line removed f.readlines() �� [string]: list of all lines read from file, end of lines removed f.seek(offset[,whence=0]) ➤ modify current position in file - whence: 0 from start, 1 from current, 2 from end f.tell() �� int: current position in file f.write(string) ➤ data written to file f.writelines(listofstrings) ➤ data written to file (no end of line added)
for line in f :�� ➤ iterate line over lines of f
Old method xreadlines replaced by iteration on file object. For optimized direct access to random lines in text files, see module linecache.
f.closed �� bool: indicator file has been closed f.encoding �� str/None: file content encoding f.name �� str: name of the file f.newlines �� str/tuple of str/None: encountered newlines chars f.softspace �� bool: indicator to use soft space with print in file
Low-level Files
Base low-level functions are in standard module os.
Careful of clash with builtins with os.open name.
open(path,flags[,mode=0777])�� int (fd): open file path - see flags infra
- mode masked out with umask
fdopen(fd[,mode[,bufsize]]) �� file: build a file connected to fd -
mode and bufsize as for builtin open()+ mode must start with r or w or a
dup(fd)�� int (fd): duplicate file descriptor fd dup2(fd,fd2)�� int (fd): duplicate file descriptor fd into fd2, previously
closing fd2 if necessary
close(fd) ➤ close file descriptor read(fd,n)�� str: read as most n bytes from fd file - return empty string if
end of file reached
write(fd,str)�� int: write str to fd file - return number of bytes actually
lseek(fd,pos,how) ➤ set file descriptor position - how: 0 from start, 1
from current, 2 from end
fdatasync(fd) ➤ flush file data to disk - don't force update metadata
fsync(fd) ➤ force low level OS buffers to be written ftruncate(fd,length) ➤ truncate file descriptor to at most length (Unix) Open Flags
Constants defined in os module, use bit-wise OR (x|y|z) to mix them.
O_RDONLY �� read only O_WRONLY �� write only O_RDWR �� read/write O_APPEND �� append each write to end O_CREAT �� create new file (remove existing) O_EXCL �� with O_CREAT, fail if file exist (Unix) O_TRUNC �� reset existing file to zero size O_DSYNC �� xxxxxx (Unix) O_RSYNC �� xxxxxx (Unix) O_SYNC �� return from IO when data are physically written (Unix) O_NDELAY �� return immediatly (don't block caller during IO) (Unix) O_NONBLOCK �� same as O_NDELAY (Unix) O_NOCTTY �� terminal device file can't become process tty (Unix) O_BINARY �� don't process end of lines (cf+lf from/to cr) (Windows) O_NOINHERIT �� xxxxxx (Windows) O_SHORT_LIVED �� xxxxxx (Windows) O_TEMPORARY �� xxxxxx (Windows) O_RANDOM �� xxxxxx (Windows) O_SEQUENTIAL �� xxxxxx (Windows) O_TEXT �� xxxxxx (Windows)
For standard process redirection using pipes, see also Simple External Process Control (p14).
os.pipe() �� ((int{2}){2}): create pair (fdmaster,fdslav) of fd
(read,write) for a pipe
os.mkfifo(path[,mode=0666]) ➤ create named pipe path - mode
masked out with umask - don't open it (Unix) Use os functions on file descriptors.
In-memory Files Memory Buffer Files
Use standard modules StringIO and cStringIO to build file-like objects storing data in memory. f = StringIO.StringIO()
Build a file-like in memory.
f.write(string) ➤ data written to file f.��other file writing methods�� f.getvalue() �� str: current data written to file f.close() ➤ file no longer usable, free buffer cStringIO is a compiled (more efficient) version of StringIO for writing. Optional argument allows to build memory files to read from too. f = cStringIO.StringIO([string]) f.read([size]) �� str: block of data read from 'file' (string) f.��other file reading methods��
Memory Mapped Files (OS level)
Standard module mmap manage memory-mapped files, usable as file-like objects and as mutable string-like objects. To build a memory map : mm = mmap.mmap(fileno,length[,tagname[,access]]) [windows] mm = mmap.mmap(fileno,length[,flags[,prot[,access]]]) [unix] Use an os file descriptor (from os.open() or from file-object's
fileno()) for a file opened for update.
Length specify amount of bytes to map. On windows, file may be extended to that length if it is shorter, it can't be empty, and 0 correspond to maximum length for the file. Access (keyword param) : ACCESS_READ (readonly),
ACCESS_WRITE (write-through, default on Windows), or ACCESS_COPY (copy-on-write).
On Windows, tagname allow to identify different mappings against same file (default to None). On Unix, flags : MAP_PRIVATE (copy-on-write private to process) or MAP_SHARED (default). And prot (memory protection mask) :
use prot+flags params, don't use access param. mm.close() ➤ mmap file no longer usable mm.find(string[,start=0])�� int: offset / -1 mm.flush([offset,size]) ➤ write changes to disk mm.move(dest,src,count) ➤ copy data in file mm.read([size])�� str: block of data read from mmap file1 mm.read_byte()�� str: next one byte from mmap file1 mm.readline()�� str: next line read from file, end of line is not removed1 mm.resize(newsize) ➤ writable mmap file resizer mm.seek(offset[,whence=0]) ➤ modify current position in mmap file - whence: 0 from start, 1 from current, 2 from end mm.size()�� int: length of the real os file mm.tell() �� int: current position in mmap file mm.write(string) ➤ data written to mmapfile1 mm.write_byte(byte) ➤ str of one char (byte) data written to mmap file1
1 File-like methods use and move file seek position.
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Files Informations
Functions to set/get files informations are in os and in os.path module, some in shutil module. Constants flags are defined in standard stat module.
Some functions accessing process environment data (ex. current working directory) are documented in Process section.
os.access(path,mode)�� bool: test for path access with mode using real
uid/gid - mode in F_OK, R_OK, W_OK, X_OK
os.F_OK �� access mode to test path existence os.R_OK �� access mode to test path readable os.W_OK �� access mode to test path writable os.X_OK �� access mode to test path executable os.chmod(path,mode) ➤ change mode of path - mode use stat.S_*
os.chown(path, uid, gid) ➤ change path owner and group (Unix) os.lchown(path, uid, gid) ➤ change path owner and group - don't
follow symlinks(Unix)
os.fstat(fd)�� int: status for file descriptor os.fstatvfs(fd)�� statvfs_result: informations about file system
containing file descriptor (Unix)
os.stat(path)�� stat structure object: file system informations (Unix) os.lstat(path)�� stat structure object: file system informations (Unix) -
dont follow symlinks
os.stat_float_times([newvalue])�� bool: test/set stat function time
stamps data type - avoid setting new value
os.statvfs(path)�� statvfs_result: informations about file system
containing path (Unix)
os.utime(path,times) ➤ set access and modification times of file path -
times=(atime,mtime) (numbers) - times=None use current time
os.fpathconf(fd,name) �� str / int: system configuration information
about file referenced by file descriptor - see platform documentation and
pathconf_names variable - name str or int (Unix)
os.pathconf(path,name)�� str / int: system configuration information
about file referenced by file descriptor - see platform documentation and
pathconf_names variable - name str or int (Unix)
os.pathconf_names �� dict: name �� index - names accepted by
pathconf and fpathconf �� corresponding index on host (Unix)
os.path.exists(path)�� bool: test existing path - no broken symlinks os.path.lexists(path)�� bool: test existing path - allow broken
os.path.getatime(path)�� float_time: last access time of path os.path.getmtime(path)�� float_time: last modification time of path os.path.getctime(path)�� float_time: creation time (windows) or last
modification time (unix) of path
os.path.getsize(path)�� int: bytes size of path file os.path.isabs(path)�� bool: test absolute os.path.isfile(path)�� bool: test regular file (follow symlinks) os.path.isdir(path)�� bool: test existing directory (follow symlinks) os.path.islink(path)�� bool: test symlink os.path.ismount(path)�� bool: test mount point os.path.samefile(path1,path2)�� bool: test refer to same real file
os.path.sameopenfile(f1,f2)�� bool: test opened files refer to same
real file (unix,macos)
os.path.samestat(stat1,stat2)�� bool: test stat tuples refer to same
file (unix,macos)
shutil.copymode(srcpath,dstpath) ➤ copy normal file permission bits shutil.copystat(srcpath,dstpath) ➤ copy normal file permission bits
and last access and modification times
Stat Structures
stat_result is returned by stat and lstat functions, usable as a
tuple and as object with attributes :
# attribute usage 0 st_mode protection bits 1 st_ino inode number # attribute usage 2 st_dev device 3 st_nlink number of hard links 4 st_uid user ID of owner 5 st_gid group ID of owner 6 st_size size of file, in bytes 7 st_atime time of most recent access 8 st_mtime time of most recent content modification 9 st_ctime time of most recent metadata change on Unix, time of creation on Windows
number of blocks allocated for file (Unix)
st_blksize filesystem blocksize (Unix) st_rdev
type of device if an inode device (Unix)
size of resource fork, in bytes(MacOS)
st_creator file creator code (MacOS) st_type
file type code (MacOS)
statvfs_result is returned by fstatvfsand statvfs functions,
usable as a tuple (use statvfs variable indexs) and as an object with attributes :
# attribute index var usage 0 f_bsize
preferred file system block size 1 f_frsize
fundamental file system block size 2 f_blocks
total number of blocks in the filesystem 3 f_bfree
total number of free blocks 4 f_bavail
free blocks available to non-super user 5 f_files
total number of file nodes 6 f_ffree
total number of free file nodes 7 f_favail
free nodes available to non-super user 8 f_flag
flags - see host statvfs() man page 9 f_namemax
maximum file name length
Stat Constants
Defined in standard stat module.
S_ISUID �� xxxxx S_ISGID �� xxxxx S_ENFMT �� xxxxx S_ISVTX �� xxxxx S_IREAD �� 00400 user can read S_IWRITE �� 00200 user can write S_IEXEC �� 00100 user can execute S_IRWXU �� 00700 user can read+write+execute S_IRUSR �� 00400 user can read S_IWUSR �� 00200 user can write S_IXUSR �� 00100 user can execute S_IRWXG �� 00070 group can read+write+execute S_IRGRP �� 00040 group can read S_IWGRP �� 00020 group can write S_IXGRP �� 00010 group can execute S_IRWXO �� 00007 everybody can read+write+execute S_IROTH �� 00004 everybody can read S_IWOTH �� 00002 everybody can write S_IXOTH �� 00001 everybody can execute
Terminal Operations
os.openpty()�� (int{2}): open pseudo-terminal1 pair
(fdmaster,fdslave)=(pty,tty) (Unix)
os.ttyname(fd)�� str: terminal device associated to fd (Unix) os.isatty(fd)�� bool: test file descriptor is a tty-like (Unix) os.tcsetpgrp(fd,pg) ➤ set process group id associted with terminal fd
os.tcgetpgrp(fd)�� int: process group associated with terminal fd
(Unix) See also standard modules tty and pty. For user-interface control on text terminal , see standard package curses and its sub- modules.
Temporary Files
Use standard tempfile module. It defines several functions to make life easier and more secure.
�� file/file-like: temp file - removed on close - not necessary visible in file- system - dir and prefix as for mkstemp
1[,suffix[,prefix[,dir]]]]]) �� file/file-like: like TemporaryFile - file visible in file-system
mkstemp([suffix[,prefix[,dir[,text]]]])�� (int,str): (fd,path) of new
temporaty file - no race condition - only creator can read/write - no executable bit - not automatically deleted - binary mode unless text specified
mkdtemp([suffix[,prefix[,dir]]])�� str: path of new temporary directory
created - no race condition - only creator can read/write/search - not automatically deleted
gettempdir() �� str: default directory for temporary files gettempprefix() �� str: default filename prefix for temporary files
Other functions in tempfile and os modules are kept for code compatibility, but are considered not enough secured. Also
tempdir and template data in tempfile - which should not be
used directly.
Path Manipulations
Path manipulation functions are in standard os.path module.
supports_unicode_filenames �� bool: unicode usable for file names
abspath(path)�� str: normalized absolutized pathname basename(path)�� str: file name part of path commonprefix(pathlist) �� str: longest common path prefix (char-by-
dirname(path)�� str: directory name of pathname join(path[,��])�� str: concatenate path components normcase(path)�� str: normalize path case for platform (see doc) normpath(path)�� str: normalize path (// /./ /../), on windows /�� \ realpath(path)�� str: canonical path (remove symlinks) (unix) split(path)�� (str{2}): split into (head, last pathname component) splitdrive(path)�� (str{2}): split into (drive, tail) splitext(path)�� (str{2}): split into (root, ext) Host Specific Path Data
sys.getfilesystemencoding() �� str: name of encoding used by
system for filenames Following data are in os and in os.path.
curdir �� str: string used to refer to current directory pardir �� str: string used to refer to parent directory sep �� str: char used to separate pathname components altsep �� str: alternative char used to separate pathname components extsep �� str: char used to separate base filename from extension pathsep �� str: conventional char to separate different paths
os.listdir(path)�� [str]/[unicode]: list names in path directory -
without . and .. - arbitrary order - path string type �� item strings type
os.mkdir(path[,mode=0777]) ➤ create directory path - mode masked
out with umask
os.makedirs(path[,mode=0777]) ➤ create directory path, recursively -
mode masked out with umask - don't handle Windows' UNC path
os.rmdir(path) ➤ remove directory path os.removedirs(path) ➤ remove directories, recursively os.walk(top[,topdown=True [,onerror=None]])�� iterable: go throught
dirs under top, for each dir yield tuple(dirpath, dirnames, filenames) - onerror=fct(os.error) - see docs
os.path.walk(path,visit,arg) ➤ call visit(arg,dirname,names) for dirs
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Special Files
os.link(src,dst) ➤ create hard link named dst referencing src (Unix) os.symlink(src,dst) ➤ create symbolic link named dst pointing to src
os.readlink(path)�� str: path pointed to by symbolic link os.mknod(path[,mode=0666,device]) ➤ create FS node (file, device
special file, named pipe) - mode = permissions | nodetype - node type in
S_IFREG, S_IFREG, S_IFCHR, S_IFBLK, and S_IFIFO defined in stat
os.major(device) �� int: raw device major number os.minor(device) �� int: raw device minor number os.makedev(major,minor) ➤ compose raw device from major and minor
Copying, Moving, Removing
os.remove(path) ➤ remove file path (not directory) os.rename(src,dst) ➤ rename src to dst - on same filesystem- may
remove existing dst file
os.renames(old,new) ➤ rename old to new, recursively - try to create
intermediate directories
os.unlink(path) ➤ remove file path (not directory) - same as remove
Standard module shutil provides high level functions on files and directories.
copyfile(src,dst) ➤ copy normal file content - overwrite destination2. copyfileobj(fsrc,fdst[,length=16kb]) ➤ copy file-like object content by
blocks of length size (<0=one chunk)
copy(src,dst) ➤ copy normal file content to file/directory2 - in case of
directory use same basename as src - overwrite destination - copy permission bits.
copy2(src,dst) ➤ same as copy + copy last access and modification
copytree(src,dst[,symlinks=False]) ➤ recursively copy directory tree -
destination must be new - files copied via copy - if symlinks is False, copy symbolic links files content, else just make symbolic links.1
rmtree(path[,ignore_errors=False[,onerror=None]]) ➤ recursively
delete directory tree - onerror=fct(fctref, path, excinfo).1
move(src,dst) ➤ recursively move file or directory tree - may rename or
1 May raise shutil.Error exception. 2 Params src and dst are files path names.
Encoded Files
Standard module codecs have functions and objects to transparently process encoded files (used internally as unicode files).
codecs.open(filename,mode[,encoding[,errors[,buffering]]])�� file-like
EncodedFile object with transparent encoding/decoding
codecs.EncodedFile(file,input[,output[,errors]]) �� file-like wrapper
around file, decode from input encoding and encode to output encoding
codecs.BOM �� str: alias for BOM_UTF16 codecs.BOM_BE �� str: alias for BOM_UTF16_BE codecs.BOM_LE �� str: alias for BOM_UTF16_LE codecs.BOM_UTF8 �� str: '\xef\xbb\xbf' codecs.BOM_UTF16 �� str: alias for BOM_UTF16_LE or BOM_UTF16_BE codecs.BOM_UTF16_BE �� str: '\xfe\xff' codecs.BOM_UTF16_LE �� str: '\xff\xfe' codecs.BOM_UTF32 �� str: alias for BOM_UTF32_LE or BOM_UTF32_BE codecs.BOM_UTF32_BE �� str: '\x00\x00\xfe\xff' codecs.BOM_UTF32_LE �� str: '\xff\xfe\x00\x00'
See Encoding - Decoding (p13) for details about encoding and errors.
Standard modules pickle and cPickle (speed up to 1000x) have support for data serialization of objects hierarchies. See Python documentation.
See also module marshal (read/write of Python data in platform independant binary format - but can broke format between releases).
Standard module shelve use pickling protocol to store objects in DBM files (see p17) and access them via a dictionnary-like interface with keys as str.
open(filename[,flag[,protocol[,writeback[,binary]]]])�� dictionary-like
object - flag as anydbm.open (p17), default to 'c' - protocol default to 0 (ascii format) - writeback: cache accessed entries in memory and written them back at close time, default to False - binary is deprecated, use protocol.
Configuration Files
Standard module ConfigParser. It uses standard .INI files to store configudation data : [section] name:value name=value
Values can contain %(name)s references which may be expanded using values in same section or in defaults
# and ; start comment lines.
Module defines 3 configuration classes with different data access level :
RawConfigParser ConfigParser SafeConfigParser
rp=RawConfigParser([defaults]) �� RawConfigParser cp=ConfigParser([defaults]) �� ConfigParser sp=SafeConfigParser([defaults]) �� SafeConfigParser In the three constructors, defaults is a dict of option:value for references expansion.
MAX_INTERPOLATION_DEPTH �� int: max recursive depth for get() when
raw parameter is false
DEFAULTSECT �� str: name of defaut section
Raw Interface
rp.defaults()�� dict: default values for references expansion rp.sections()�� [string]: list sections in config (without DEFAULT) rp.add_section(section) ➤ add a new section - may raise
rp.has_section(section)�� bool: test if section exists - cant test for DEFAULT rp.options(section)�� [string]: list options in section rp.has_option(section,option)�� bool: test if section and option exists rp.read([filename]/filename)�� [filename]: try to load configuration data from files (continue if fail) - return names of loaded files rp.readfp(fp[,filename]) ➤ load configuration data from file/file-like rp.get(section,option)�� str: option value rp.getint(section,option)�� int: coerce option value to int rp.getfloat(section,option)�� float: coerce option value to float rp.getboolean(section,option)�� bool: coerce option value to bool -
True is strings 1 yes true on - False is strings 0 no false off - may
raise ValueError rp.items(section)��[(name,value)]: options in the section rp.set(section,option,value) ➤ set option to string value in section - may raise NoSectionError rp.write(fileobject) ➤ write configuration data to file rp.remove_option(section,option)�� bool: return True if there was such option - may raise NoSectionError rp.remove_section(section)�� bool: return True if there was such section rp.optionxform(option)�� str: normalized internal form of option
Normal Interface
cp.get(section,option[,raw[,vars]])�� string: value for option in section - % interpolation expanded unless raw is true - vars is a dict of additional defaults - reference expansion names are processed by optionxform() for matching cp.items(section[,raw[,vars]])�� [(name,value)]: for given section - raw and vars as in get()
Safe Interface
sp.set(section,option,value) ➤ set value string for section and option
Error ParsingError NoSectionError DuplicateSectionError MissingSectionHeaderError NoOptionError InterpolationError InterpolationDepthError InterpolationMissingOptionError InterpolationSyntaxError
For similar file format supporting nested subsections, see
ConfigObj config parser. For windows users, standard module _winreg.
For text-file configs, can use XML tools, and see also third party YAML parsers like PyYaml.
Standard exceptions defined in exceptions module, and available in current scope. All exceptions must be subclasses of Exception root class.
Use standard exceptions if their meaning correspond to you errors. Subclass standard exceptions when needed.
Standard Exception Classes
Exception StopIteration �� iterator's next(), no more value. SystemExit �� sys.exit() called StandardError �� built-in exceptions ArithmeticError �� arithmetic errors. FloatingPointError OverflowError ZeroDivisionError AssertionError �� assert cond[,message] failed. AttributeError �� attribute set/get failed. EnvironmentError �� host system error - see arg tuple attribute IOError OSError WindowsError �� Windows error codes. EOFError �� end-of-file with input() or raw_input(). ImportError KeyboardInterrupt �� user interrupt (Ctrl-C). LookupError IndexError �� non-existent sequence index. KeyError �� non-existent mapping key. MemoryError NameError �� non-existent name in current scope. UnboundLocalError �� reference to an unassigned local
ReferenceError �� try accessing weak-ref disposed object. RuntimeError �� (prefer defining ad-hoc subclasses). NotImplementedError SyntaxError IndentationError TabError SystemError �� a bug�� in Python. TypeError ValueError �� good type, but bad value. UnicodeError Warning �� warnings superclass (see Warnings infra) UserWarning
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PendingDeprecationWarning DeprecationWarning SyntaxWarning RuntimeWarning
Warnings must be subclasses of Warning root class. Standard warnings module control processing of warning exceptions.
warn(message[,category[,stacklevel]]) warn_explicit(message,category,filename,lineno[,module[,registry]
showwarning(message,category,filename,lineno[,file]) formatwarning(message,category,filename,lineno) filterwarnings(action[,message[,category[,module[,lineno[,append]
Exceptions Processing
sys.exc_info()�� (type,value,traceback) for current exception1 sys.exc_clear() ➤ current exception related informations cleared sys.excepthook �� (rw) fct(type, value, traceback) called for uncaught
sys.__excepthook__ �� backup of original excepthook function sys.tracebacklimit �� int: (rw) maximum levels of traceback printed,
<=0 for none
1 Or (None,None,None) if no running exception.
Standard module traceback has tools to process and format these informations.
Standard module codecs provide base support for encoding / decoding data. This is used for character encodings, but also for data compression (zip, bz2) or data representation (uu, hex). See Unicode strings (p5), Source encodings (p3). See functions, classes and constants for files encoding in Encoded Files (p12). Module encodings.aliases.
Python threads use native threads. A global mutex (the GIL) lock interpreter data during Python virtual instructions execution (it is unlocked during I/O or long computation in native code). Check for thread switching and signal processing is performed at regular interval.
sys.getcheckinterval()�� int: current thread switching check
sys.setcheckinterval(interval) ➤ set hread switching check interval1
1 Expressed in number of Python virtual instructions.
Threading Functions
Use standard high level module threading which provides several classes : Thread, local (for thread local storage), Event, Lock and
RLock (mutex), Semaphore and BoudedSemaphore, Timer.
Module threading also provides functions :
activeCount()�� int: number of currently active threads currentThread()�� Thread: current running thread enumerate()�� [Thread]: list of active threads settrace(func) ➤ install trace function called before threads run
setprofile(func) ➤ install profile function called before threads run
Standard module thread supports low level thread management. Use modules dummy_thread and dummy_threading on platforms without multithreading.
Class threading.Thread is used to create new execution path in current process. It must be called with keyword arguments. Specify thread code with a callable target param or by overriding run method (remember calling inherited __init__ in subclasses), give arguments in args and kwargs (tuple and dict), give a name to identify the thread - group currently not used (None). th = threading.Thread(group,target,name,args,kwargs) th.start() ➤ start thread activity (in another thread) th.run() ➤ thread code to execute - call target if not overriden th.join([timeout]) ➤ wait for th termination or timeout elapsed (float_delay, default to None for infinite) th.getName()�� str: thread associated name th.setName(name) ➤ set thread associated name (initial name set by class) th.isAlive()�� bool: test thread alive (started and run() not terminated) th.isDaemon()�� bool: test thread have daemon flag th.setDaemon(daemonic) ➤ set thread daemon flag - must be called before start. Initial flag inherited from creating thread. Python process exit only after last non-daemon thread termination.
A thread can't be killed or paused externally by another thread.
Thread Local Storage
Class threading.local attributes values are thread local. Subclass it or use it as a namespace. tlsdata = threading.local() tlsdata.x = 1
Delayed Start Thread
Class threading.Timer is a subclass of Thread which effectively run after a specified interval from its start. t = threading.Timer(interval,function,args=[],kwargs={}) t.cancel() ➤ timer will never run - must not be already running Create a timer that will run function with arguments args and keyword arguments kwargs, after interval seconds have passed.
Mutual Exclusion
Classes threading.Lock and threading.RLock provide mutual exclusion between threads. Lock doesn't allow a thread to re- acquire a lock it already owns, RLock does (reentrant-lock). lock = threading.Lock() lock = threading.RLock() lock.acquire([blocking])�� bool/None: acquire the lock. blocking unspecified : wait & return None ; blocking true : wait & return True ; blocking false : don't wait (try) & return True/False lock.release() ➤ unlock a previously acquired lock Must release a lock same times as it was acquired. Good practice to acquire/release locks in try/finally blocks. For portable inter-process mutex, see third party glock.py module.
Class threading.Event is a synchronisation flag with thread blocking mechanism to wait for the flag. evt = threading.Event() ➤ new event, with internal flag set to False evt.isSet()�� bool: value of event internal flag evt.set() ➤ set event internal flag to true - unlock waiting threads evt.clear() ➤ set event internal flag to False evt.wait([timeout]) ➤ wait for event internal flag to be true - timeout is a float_delay (default to None=infinite blocking)
General purpose events scheduler
Module sched provides such a tool, adaptable to your needs ('time' unit is yours). sc = sched.scheduler(timefunc,delayfunc) �� scheduler: timefunc return numbers mesuring time, delayfunc(n) wait n time (same unit as timefunc output) - typically sc =
sc.enterabs(time,priority,action,args) �� evtid: schedule a new event, will call action(*args) at time sc.enter(delay,priority,action,args)�� evtid: schedule a new event, will call action(*args) after delay sc.cancel(evtid)➤ remove scheduled event - may raise RuntimeError sc.empty()�� bool: test if scheduler events queue is empty sc.run()➤ run scheduled events at their scheduling time - see docs
Classes threading.Semaphore and threading.BoundedSemaphore provide simple semaphore for resources counting (without/with counter checking). sem = threading.Semaphore([value=1]) ➤ semaphore with initial counter sem = threading.BoundedSemaphore([value]) sem.acquire([blocking])�� bool/None: acquire the semaphore (consume one resource). blocking unspecified : wait & return None ; blocking true : wait & return True ; blocking false : don't wait (try) & return True/False sem.release() ➤ release the semaphore (free one resource)
Condition Variables
Class threading.Condition allows threads to share state (data) protected via a Lock. Important : condition variables (lock) must be acquired when calling wait, notify or notifyAll. See Python docs. cond = threading.Condition([lock]) ➤ build new condition variable, use user providen lock (Lock or RLock) else build a new RLock cond.acquire(*args)�� value: acquire cond. var. lock, return lock.acquire() value cond.release() ➤ release cond. var. lock cond.wait([timeout]) ➤ wait until notified or timeout elapsed- timeout is a float_delay (default to None=infinite blocking). Release cond. var. lock and wait for a notification/timeout then re-acquire lock. cond.notify() ➤ wake up one waiting thread (if any). cond.notifyAll() ➤ wake up all waiting threads.
Synchronized Queues
Module Queue provides a class Queue to store data in a synchronized FIFO queue, and two exception classes Full and
Empty. In blocking mode, full queue block producers and empty
queue block consumers (in non-blocking mode they raise exceptions). Other organization can be built with subclassing (see source for internal methods). q = queue.Queue(maxsize) ➤ build new queue - infinite queue if maxsize<=0 q.qsize()�� int: size of the queue - at call time q.empty()�� bool: test if queue size if 0 - at call time q.full()�� bool: test if queue size is maxsize - at call time q.put(item[,block[,timeout]]) ➤ put item in queue - block can be true/false, timeout can be None/float_delay. May raise Queue.Full exception. q.put_nowait(item) ➤ same as put(item,False) q.get([block[,timeout]])�� item: removed from queue - block can be true/false, timeout can be None/float_delay - may raise Queue.Empty exception q.get_nowait() ➤ same as get(False)
Current Process
Standard module os has tools to get information about and manipulate current process and its environment.
Normally Python process exit when there is no more non-daemon thread running.
sys.exit([arg=0]) ➤ exit via a SystemExit exception (may be catch) -
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os._exit(n) ➤ exit without cleanup os.abort() ➤ exit via a SIGABRT signal (signal may be handled)
Following exit codes are defined in os (Unix) :
no error
command used incorrectly
incorrect input data
unavailable/inaccessible input
unknown user
unknown host
required service unavailable
internal error
OS error
missing/inaccessible file
can't create output
error during file I/O
temporary failure
illegal/invalid/not understood protocol exchange
not enough permissions (out of file perms)
configuration problem
missing data You can install exit functions (for normal exit) with module atexit.
register(func[,*args[,**kargs]]) ➤ register function to be called with args
and kargs Registered functions are called in reverse order of registration. Bypassed when process is terminated by a signal, an internal error, or an os._exit.
Environment Variables
environ �� dict: environment variables - modification call putenv if
getenv(varname[,default=None])�� str: environment variable value putenv(varname,value) ➤ set environment variable - affect later started
subprocess - may cause memory leaks (see platform documentation) Some functions also in os.path :
expanduser(path)�� str: path with initial "~" or "~user" replaced expandvars(string)�� str: string with $name or ${name} environment
variable replaced
Directory, Files, Terminal
See also Console & Interactive Input/Output (p2), and Files - Terminal Operations (p11).
chdir(path) ➤ change current working directory to path fchdir(fd) ➤ change current working directory to thus represented by file
getcwd()�� str: current working directory getcwdu()�� unicode: current working directory chroot(path) ➤ change process file-system root to path (Unix) umask(mask)�� int: set current numeric umask and return previous one ctermid()�� str: filename of controlling terminal (Unix) getlogin()�� str: name of user logged on controlling terminal (Unix) User, process, group IDs
pid: process id, gid: group id, uid: user id
getpid()�� int: current pid getegid()�� int: effective gid (Unix) setegid(egid) ➤ set process effective gid (Unix) geteuid()�� int: effective uid (Unix) seteuid(euid) ➤ set process effective uid (Unix) getgid()�� int: real gid (Unix) setgid(gid) ➤ set process gid (Unix) getuid()�� int: current process' uid (Unix) setuid(uid) ➤ set process current uid (Unix) setregid(rgid,egid) ➤ set process real and effective gid (Unix) setreuid(ruid,euid) ➤ set process real and effective uid (Unix) getpgrp()�� int: current gid (Unix) getgroups()�� [int]: list of supplemental associated gid (Unix) setgroups(groups) ➤ set list of supplemental associated gid (Unix) setpgrp() ➤ call system function1 (Unix) getppid()�� int: parent's pid (Unix) setsid() ➤ call system function1 (Unix) getpgid(pid)�� int: process group id of process id pid (0=current) (Unix) getsid(pid) ➤ call system function1 (Unix) setpgid(pid,pgrp) ➤ set process pid group to pgrp1 (Unix)
1 See manual for semantics.
Timings, Priority times()�� (ut,st,cut,cst,ert): (float_delay{5}): user time, system time,
children's user time, children's system time, elapsed real time
nice(increment)�� int: renice process - return new niceness (Unix) Memory plock(op) ➤ lock program segments into memory - see <sys/lock.h> for
op values (Unix)
Host Informations strerror(code)�� str: error message for the error code uname()�� tuple: current operating system identification, (sysname,
nodename, release, version, machine) (recent Unix)
sys.byteorder �� str: host native byte order big or little sys.winver �� str: version number for registry keys (Windows) sys.platform �� str: platform identifier (ex. linux2)
Following data are in os and in os.path.
defpath �� str: search path for os.exec*p*() and os.spawn*p*() if
environment PATH not defined
linesep �� str: end of line char(s) for the plaftorm devnull �� str: file path of null device
Python Informations
sys.builtin_module_names �� (str): names of modules compiled into
sys.copyright �� str: copyright of interpreter sys.hexversion �� int: Python version with one digit by byte sys.version �� str: interpreter version + build + compiler sys.dllhandle �� int: handle of Python DLL (Windows) sys.executable �� str: name of interpreter executable binary sys.prefix �� str: directory prefix for platform independant Python files sys.api_version �� int: version of Python C API sys.version_info �� (int{3},str,int): (major, minor, micro,
releaselevel, serial) - release in alpha, beta, candidate, final
Signal Handling
Standard module signal. See doc for general rules about signals usage in Python. Signal handlers are callable f(signalnum,stackframe).
alarm(time)�� float_delay: previous alarm remaining time - request a new
SIGALRM in time seconds - cancel previous one - time��0 (Unix)
alarm(0)�� float_delay: previous alarm remaining time - cancel previous
alarm (Unix)
getsignal(signalnum)�� fct: current signal handler or SIG_IGN or SIG_DFL
or None (handler not installed from Python)
pause() ➤ sleep process until a signal is received (Unix) signal(signalnum,handler)�� fct: previous handler for signal (as getsignal) - install new handler (maybe SIG_IGN or SIG_DFL too) - only
callable in main thread Following signal constants are defined :
SIG_DFL �� 0: default signal handler function SIG_IGN �� 1: ignore signal handler function NSIG �� int: highest signal number +1
Module also defines signal numbers (Posix examples - runtime definition is platform dependant) :
terminal or control processus disconnection
keyboard interrupt
quit request from keyboard
illegal instruction
abort stop signal
floating point error
the KILL signal
invalid memory reference
pipe write without reader
alarm timer elapsed
termination signal
user signal 1
user signal 2
terminated/stopped child
continue process (if stopped)
stop process
stop request from keyboard
read on tty while in background
write on tty while in background �� �� see your platform documentation (man 7 signal on Linux). Functions to send signals are in os module :
kill(pid,sig) ➤ kill process pid with signal sig (Unix) killpg(pgid,sig) ➤ kill process group pgid with signal sig (Unix) Simple External Process Control
Use standard module subprocess. It wraps external process creation and control in Popen objects. Child process exceptions raised before execution are re-raised in parent process, exceptions will have child_traceback attribute (string). Note : subprocess tools will never call /bin/sh implicitly.
PIPE �� -1: constant value used for Popen stdin stdout stderr params
call(*args,**kwargs)�� int: run command with arguments, wait for
completion, return retcode - convenient wrapper around Popen object Use Popen objects as process control tools : p =
args is a string/list of strings ["command","arg1","arg2",��] bufsize like for file/open functions executable can be used to provide command in place of args[0] stdin, stdout and stderr can be PIPE to capture file and communicate with subprocess preexec_fn is called just before child process execution close_fds bool force subprocess inherited files to be closed, except 0 1 and 2 shell bool force execution of command throught the shell cwd string specify working directory to set for subprocess start env dictionnary specify environment variables for subprocess universal_newlines translate all newlines to \n (like U mode for files) startupinfo and creationflags are optional informations for process creation under Windows p.poll()�� int/None: check child process termination, return returncode attribute p.wait()�� int: wait for child process to terminate, return returncode attribute p.communicate(input=None)�� (stdout,stderr): send data (input string)to stdin, read data from stdout/stderr until end-of-file, wait process to terminate, return read values - data read is buffered in memory p.stdin �� file/None: standard input from chil process if captured p.stdout �� file/None: standard output from chil process if captured p.stderr �� file/None: error output from chil process if captured 14a 14b 14c

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p.pid �� int: process ID of child process p.returncode �� int/None: child process return code (None if not terminated) - on Unix -N for subprocess terminated by signal N
Use subprocess module when possible (cleaner, simpler interface, see docs for examples). See also external module pexpect.
Advanced External Process Control
See following functions from os module.
execl(path,[arg[,��]]) execle(path,[arg[,��]],env) execlp(file,[arg[,��]]) execlpe(file,[arg[,��]],env) execv(path,args) execve(path,args,env) execvp(file,args) execvpe(file,args,env)
With exec�� new program replace current process (fct don't return). 'p' versions use PATH to locate executable file. 'e' versions use a dict env to setup new program environment. 'l' versions use a positioned arg, 'v' versions use list of variable args.
spawnl(mode,path,[arg[,��]])�� int spawnle(mode,path,[arg[,��]],env) �� int spawnlp(mode,file,[arg[,��]])�� int spawnlpe(mode,file,[arg[,��]],env) �� int spawnv(mode,path,args) �� int spawnve(mode,path,args,env) �� int spawnvp(mode,file,args) �� int spawnvpe(mode,file,args,env) �� int
With spawn�� new process is created. 'lpev' versions like for exec��. If mode is P_NOWAIT or P_NOWAIT0, return child pid (Unix) or process handle (Windows). If mode is P_WAIT, wait child termination and return its exit code (>0) or its killing signal (<0). On Windows mode can be, P_DETACH (same as P_NOWAIT but new process detached from calling process console) or P_OVERLAY (current process is replaced).
fork()�� pid: fork a child process, return 0 in child, child pid in parent
forkpty()�� (int{2}): (pid,fd): fork using new pseudo-terminal for child -
pid is 0 in child, child pid in parent - fd pseudo-terminal master end (Unix)
startfile(path) ➤ open file path as if double-clicked in explorer
system(cmd)�� value: execute string cmd in subshell - generally return
(pid/status) (Unix) or status (Windows)
wait()�� (int{2}): (pid,status) wait completion of a child process (Unix)
- status=0xZZTT where ZZ=exit code, TT=signal num
waitpid(pid,options)�� (int{2}): (pid,status) (Unix):
pid>0 wait for specific process, pid=0 wait for any child in process group, pid=-1 wait for any child of current process, pid<-1 wait for any process in process group -pid option in WNOHANG, WCONTINUED, WUNTRACED status=0xZZTT where ZZ=exit code, TT=signal num
waitpid(pid,options)�� (int{2}): (pid,status) (Windows): pid is any
process handle (>0) - option ignored - status=0xZZ00 where ZZ=exit code
Status informations extraction WCOREDUMP(status)�� bool: test process generated core-dump (Unix) WIFCONTINUED(status)�� bool: test process continued from a job control
stop (Unix)
WIFSTOPPED(status)�� bool: test process stopped (Unix) WIFSIGNALED(status)�� bool: test exited on signal (Unix) WIFEXITED(status)�� bool: test process exited via exit(2) system call
WEXITSTATUS(status)�� int: if exited via exit(2), return exit parameter
WSTOPSIG(status)�� int: signal having stopped process (Unix) WTERMSIG(status)�� int: signal having exited process (Unix) Pipes On Process
Three functions available in popen2 module (and in os module where stdin/stdout return values are inverted).
popen2(cmd[,bufsize[,mode]])�� (file{2}): (stdout,stdin): execute
cmd as sub-process
popen3(cmd[,bufsize[,mode]])�� (file{3}): (stdout,stdin,stderr):
execute cmd as sub-process
popen4(cmd[,bufsize[,mode]])�� (file{2}): stdout_stderr,stdin):
execute cmd as sub-process Where bufsize is buffer size for I/O pipes, and mode is 'b' (binary streams) or 't' (text streams, default). Param cmd is a string passed to os.system - on Unix it can be a sequence of strings passed directly to the program without shell intervention. On Unix, popen2 module also defines Popen3 class (used in popen2 and popen3 functions) and Popen4 class (used in popen4 function) :
Popen3(cmd[,capturestderr[,bufsize]])�� Popen3: cmd: str shell
command, captudestderr: bool (default False)
Popen4(cmd[,bufsize])�� Popen4
Popen3 and Popen4 objects have following attributes : p.poll()�� int: child return code or -1 if child not terminated p.wait()�� int: child return code p.fromchild �� file: output from child (stdout and stderr for Popen4) p.tochild �� file: input to child p.childerr �� file: error output from child if requested else None (None for Popen4) p.pid �� int: child process pid See also module commands (Unix).
Several modules to process XML are available. Some with standard SAX and DOM interfaces, others with more Pythonic interfaces. See also third party PyXML extension package.
SAX - Event-driven
Base functions in xml.sax module.
make_parser([parser_list]) �� XMLReader: built from first parser
parse(filename_or_stream,content_handler[,error_handler]) ➤ parse
document using first parser available
parseString(string,content_handler[,error_handler]) ➤ parse string
using first parser available
XMLReader Interface
Defined in xml.sax.xmlreader. p = xml.sax.make_parser() �� XMLReader object p.parse(source) ➤ completly parse source - source is filename or URL or file-like or InputSource- input byte streams (not character streams) p.getContentHandler() �� ContentHandler: current one p.setContentHandler(handler) ➤ set current content handler p.getDTDHandler() �� DTDHandler: current one p.setDTDHandler(handler) ➤ set current DTD handler p.getEntityResolver() �� EntityResolver: current one p.setEntityResolver(handler) ➤ set current entity resolver p.getErrorHandler() �� ErrorHandler: current one p.setErrorHandler(handler) ➤ set current error handler p.setLocale(locale) ➤ set locale for errors and warnings p.getFeature(featurename) �� current settings for feature1 p.setFeature(featurename,value) ➤ set feature to value p.getProperty(propertyname) �� current settings for property2 p.setProperty(propertyname,value) ➤ set property to value There is also an IncrementalParser subclass interface with : p.feed(data) ➤ process a chunk of data p.close() ➤ assume end of document, check well-formedness, cleanup p.reset() ➤ after close, prepare new parsing
1 Feature names in xml.sax.handler as feature_xxx. 2 Property names in xml.sax.handler as property_xxx.
InputSource Interface
Provide source of data for parser. isrc.setPublicId(id) ➤ set public identifier isrc.getPublicId() �� unicode: public identifier isrc.setSystemId(id) ➤ set system identifier isrc.getSystemId() �� unicode: system identifier isrc.setEncoding(encoding) ➤ set encoding - must be a string acceptable for an XML encoding declaration - ignored if InputSource contains character stream isrc.getEncoding() �� str/None (if unknown) isrc.setByteStream(bytefile) ➤ set input byte stream - ignored if InputSource contains character stream isrc.getByteStream() �� byte stream isrc.setCharacterStream(charfile) ➤ set character (Unicode) stream isrc.getCharacterStream() �� character stream
Locator Interface
Instances of Locator provide these methods: loc.getColumnNumber() �� int: column number where current event ends loc.getLineNumber() �� int: line number where current event ends loc.getPublicId() �� str: public identifier of current event loc.getSystemId() �� str: system identifier of current event
Attributes Interface
Also implement parts mapping protocol (copy(), get(), has_key(),
items(), keys(), and values()).
ai.getLength() �� int: number of attributes ai.getNames() �� [unicode]: names of attributes ai.getType(name)�� type of attribute name - normally 'CDATA' ai.getValue(name)�� unicode: value of attribute name
AttributesNS Interface
Also implement Attributes interface. ansi.getValueByQName(name)�� unicode: value of attribute qualified name ansi.getNameByQName(name)�� (unicode{2}): (namespace, localname) for qualified name ansi.getQNameByName(namepair)�� unicode: qualified name for (namespace, localname) ansi.getQNames()�� [unicode]: qualified names of all attributes
ContentHandler Interface
Defined in xml.sax.handler. Its methods are handlers called when parser find XML structures. ch = MyContentHandler() �� ContentHandler subclass object ch.setDocumentLocator(locator) ➤ set locator for origin of document events ch.startDocument() ➤ beginning of document ch.endDocument() ➤ end of document ch.startPrefixMapping(prefix,uri) ➤ begin of a prefix-URI namespace mapping - see doc ch.endPrefixMapping(prefix) ➤ end of a prefix-URI namespace mapping ch.startElement(name,attrs) ➤ start of an element - non-namespace mode - attrs has an Attributes interface (may be reused - copy data) ch.endElement(name) ➤ end of an element - non-namespace mode ch.startElementNS(name,qname,attrs) ➤ start of an element - namespace mode - name is (uri,localname) - qname is raw XML name - attrs has an AttributesNS interface (may be reused - copy data) - qname may be None (upon feature_namespace_prefixes) ch.endElementNS(name,qname) ➤ end of an element - namespace mode ch.characters(content) ➤ character data - content is str or unicode 15a 15b 15c

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ch.ignorableWhitespace(whitespace) ➤ whitespaces ch.processingInstruction(target,data) ➤ processing instruction ch.skippedEntity(name) ➤ entity not processed
DTDHandler Interface
Defined in xml.sax.handler. Its methods are handlers called when parser need DTD relative work. dh = MyDTDHandler() �� DTDHandler subclass object dh.notationDecl(name,publicId,systemId) ➤ notation declaration dh.unparsedEntityDecl(name,publicId,systemId,ndata) ➤ unparsed entity declaration
EntityResolver Interface
Defined in xml.sax.handler. Its methods are handlers called when parser need external entity resolution. er = MyEntityResolver() �� EntityResolver interface object er.resolveEntity(publicId,systemId) �� str/InputSource: default return systemId
Defined in xml.sax module.
SAXException(msg[,exception]) SAXParseException(msg,exception,locator) �� invalid XML SAXNotRecognizedException(msg[,exception]) SAXNotSupportedException(msg[,exception])
ErrorHandler Interface
Defined in xml.sax.handler. Its methods are handlers called when parser detect an error. Their exception parameters get
SAXParseException objects.
eh = MyErroHandler() �� ErrorHandler interface object eh.error(exception) ➤ recovererable error - parsing will continue if method return eh.fatalError(exception) ➤ unrecoverable error - parsing must stop eh.warning(exception) ➤ minor warning - parsing will continue if method return
SAX Utilities
Defined in xml.sax.saxutils.
escape(data[,entities]) �� str: & < > escaped - escape other entities
replacing mapping strings (keys) by corresponding identifiers
unescape(data[,entities]) �� str: &amp; &lt; &gt; unescaped -
unescape other entities replacing mapping identifiers (keys) by corresponding strings
quoteattr(data[,entities]) �� str: as escape + quote string to be used
as attribute value
prepare_input_source(source[,base]) �� InputSource: source is
string, file-like, or InputSource - base is an URL string - return
InputSource for parser
Class XMLGenerator is a ContentHandler writing SAX events into an XML document (ie. reproduce original document).
XMLGenerator([out[,encoding]]) �� content handler: out file-like, deault
to sys.stdout - encoding default to 'iso-8859-1' Class XMLFilterBase is a default pass-throught events, can be subclassed to modify events on-fly before their processing by application handlers.
XMLFilterBase(base) �� events filter Features & Properties
Defined in xml.sax.handler. Dont give their value, but their meaning.
feature_namespaces1 �� True: perform namespace processing. False:
no namespace processing (so no namespace prefixes).
feature_namespace_prefixes1 �� True: report original prefixed names
and attributes used for namespace declarations.
feature_string_interning1 �� True: intern all names (elements,
prefixes, attributes, namespace URIs, local names).
feature_validation1 �� True: report all validation errors. feature_external_ges1 �� True: include all external general (text)
feature_external_pes1 �� True: include all external parameter entities,
including the external DTD subset.
all_features �� list of all features property_lexical_handler �� optional extension handler for lexical
events (like comments).
property_declaration_handler �� optional extension handler for DTD-
related events other than notations and unparsed entities.
property_dom_node1 �� visited DOM node (if DOM iterator) when parsing,
else root DOM node.
property_xml_string �� literal string source of current event (read only
all_properties �� list of all properties names
1 can only be read during parsing (and modified before).
DOM - In-memory Tree
Defined in xml.dom. Two function to register/access DOM processors, and some constants.
registerDOMImplementation(name,factory) ➤ register DOM
implementation factory
getDOMImplementation([name[,features]]) �� DOM implementation -
name may be None - may found name in env. var PYTHON_DOM - features is [(featurename,version),��]
EMPTY_NAMESPACE �� no namespace associated with a node XML_NAMESPACE �� xml prefix namespace XMLNS_NAMESPACE �� namespace URI for namespace declarations - DOM
level 2 specification definition
impl.hasFeature(feature,version) �� bool: test for supported feature in an implementation
Defined in xml.dom, class Node is parent of XML components nodes classes. o.nodeType �� int: (ro) in ELEMENT_NODE, ATTRIBUTE_NODE,
o.parentNode �� Node/None: (ro) - None for Attr nodes o.attributes �� NamedNodeMap/None: attribute objects for elements, else None o.previousSibling �� Node/None: (ro) previous node in parent's children o.nextSibling �� Node/None: (ro) next node in parent's children o.childNodes �� [Node]: (ro) list of subnodes o.firstChild �� Node/None: (ro) first subnode o.lastChild �� Node/None: (ro) last subnode o.localName �� unicode/None: (ro) element name without namespace prefix o.prefix �� unicode/None: (ro) element namespace prefix - may be empty string or None o.namespaceURI �� unicode/None: (ro) URI associated to element namespace o.nodeName �� unicode/None: (ro) usage specified in subclasses o.nodeValue �� unicode/None: (ro) usage specified in subclasses o.hasAttributes() �� bool: test any attribute existence o.hasChildNodes() �� bool: test any subnode existence o.isSameNode(other) �� bool: test other refers same node o.appendChild(newChild) �� new Child: add new child node at end of subnodes - return new child o.insertBefore(newChild,refChild) �� new Child: add new child node before an existing subnode - at end of subnodes if refChild is None - return new child o.removeChild(oldChild) �� oldChild: remove a subnode, return it - when no longer used, must call oldChild.unlink() o.replaceChild(newChild,oldChild) ➤ replace existing subnode with a new one o.normalize() ➤ join adjacent text nodes o.cloneNode(deep) �� Node: if deep, clone subnodes too - return clone
A sequence of nodes, usable as a Python sequence (maybe modifiable upon implementation). o.length �� int: number of nodes in the sequence o.item(i) �� Node/None: ith item in the list
Subclass of Node. o.nodeType �� DOCUMENT_TYPE_NODE o.publicId �� unicode/None: public identifier for external subset of DTD o.systemId �� unicode/None: system identifier URI for external subset of DTD o.internalSubset �� unicode/None: complete internal subset from the document - without brackets o.name �� unicode/None: name of root element (as given in DOCTYPE) o.entities �� NamedNodeMap/None: definition of external entities o.notations �� NamedNodeMap/None: definition of notations
Subclass of Node. o.nodeType �� DOCUMENT_NODE o.documentElement �� Element: root element of the document o.createElement(tagName)�� Element: new1 element node o.createElementNS(namespaceURI,tagName)�� Element: new1 element node with namespace - tagName may have prefix o.createTextNode(data) �� Element: new1 text node containing data o.createComment(data) �� Element: new1 comment node containing data o.createProcessingInstruction(target,data) �� Element: new1 processing instruction node containing target and data o.createAttribute(name) �� Element: new1 attribute node o.createAttributeNS(namespaceURI,qualifiedName) �� Element: new1 attribute node with namespace - tagName may have prefix o.getElementsByTagName(tagName) �� NodeList: search for all descendants (deep search) having type tagName o.getElementsByTagNameNS(namespaceURI,localName) �� NodeList: search for all descendants (deep search) having namespaceURI and localName (part after prefix)
1 New nodes are standalone - you must insert/associate them in/to
document parts.
Subclass of Node. o.nodeType �� ELEMENT_NODE o.tagName �� unicode: element type name - with namespace may contain colons o.getElementsByTagName(tagName) �� NodeList: search for all descendants (deep search) having type tagName o.getElementsByTagNameNS(namespaceURI,localName) �� NodeList: search for all descendants (deep search) having namespaceURI and localName (part after prefix) o.getAttribute(attname)�� unicode: attribute value o.getAttributeNode(attrname)�� Attr: attribute node o.getAttributeNS(namespaceURI,localName)�� unicode: attribute value o.getAttributeNodeNS(namespaceURI,localName)�� Attr: attribute node o.removeAttribute(attname) ➤ remove attribute by name - ignore missing attribute o.removeAttributeNode(oldAttr)�� Attr: remove and return oldAttr o.removeAttributeNS(namespaceURI,localName) ➤ remove attribute 16a 16b 16c

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by namespace URI and name - ignore missing attribute o.setAttribute(attname,value) ➤ set attribute string value o.setAttributeNode(newAttr)�� Attr: set attribute from a new Attr node - return old one o.setAttributeNodeNS(newAttr)�� Attr: set attribute from a new Attr node with namespace URI and local name - return old one o.setAttributeNS(namespaceURI,qname,value)�� Attr: set attribute string value from a namespaceURI and qname (whole attribute name) - return old one
Subclass of Node. o.nodeType �� ATTRIBUTE_NODE o.name �� unicode: (ro) attribute full name - may have colons o.localName �� unicode: (ro) attribute name - part after colons o.prefix �� unicode: (ro) attribute prefix - part before colons - may be empty
A mapping of nodes - experimentally usable as a Python mapping. o.length �� int: length of attributes list o.item(index) �� Attr: attribute at index - arbitrary but consistent order
Subclass of Node. Cannot have subnode. o.nodeType �� COMMENT_NODE o.data �� unicode: content of the comment, without <!-- and -->
Subclasses of Node. Cannot have subnode. Text part in an element. o.nodeType �� TEXT_NODE o.data �� unicode: text content
Subclasses of Node. Cannot have subnode. CDATA section in a document, may have multiple CDATASection nodes for one CDATA. o.nodeType �� CDATA_SECTION_NODE o.data �� unicode: CDATA content
Subclasses of Node. Cannot have subnode. Represents a processing instruction in the XML document; this inherits from the Node interface and cannot have child nodes. o.nodeType �� PROCESSING_INSTRUCTION_NODE o.target �� unicode: (ro) processing instruction content up to first whitespace o.data �� unicode: (ro) processing instruction content after first whitespace
Python map DOM error codes to exceptions.
DOM codes constants Exception
exception.code �� int: DOM code corresponding to exception exception.msg �� string: message for exception
DOMException DomstringSizeErr �� implementation limit reach HierarchyRequestErr �� insert at wrong place IndexSizeErr �� index range error InuseAttributeErr �� Attr node already used in tree InvalidAccessErr �� param/operation unsupported by object InvalidCharacterErr �� character invalid in the context InvalidModificationErr �� can't modify node type InvalidStateErr �� try to use an undefined/unusable object NamespaceErr �� change forbidden in namespace context NotFoundErr �� node don't exist in referenced context NotSupportedErr �� operation/type unsupported by
NoDataAllowedErr �� no data for this node NoModificationAllowedErr �� can't modify object SyntaxErr �� invalide/illegal string WrongDocumentErr �� impl. can't migrate nodes between docs
See Python.org wiki for a list of database interface modules. Some interfaces are for external DB engines (MySQL, PostgreSQL, BerkeleyDB, SQLite, Metakit��), other for pure Python DB engines (gadfly, ZODB, KirkyBase, Buzhug��).
Generic access to DBM-style DBs
Standard module anydbm is a front-end to some available DB modules : dbhash (��bsddb��Berkeley DB), gdbm (��GNU dbm), dbm (��unix dbm) and the slow portable fallback dumbdbm. Data stored in DBM-style files are accessed via a dictionary-like interface where keys and values must be str.
open(filename[,flag[,mode]]) �� dictionary-like object: flag in 'r' (read-
default), 'w' (write), 'c' (create if doesn't exist), 'n' (create new empty) - mode is unix mode flags for creation
error �� tuple of exception classes from DB modules (anydbm.error,��)
Uses module whichdb to identify right DB module for existing file. For new files, use first available DB module in the order of the list. This is used by shelve module (see Persistence, p12). DB modules can have specific functions related to their backend, see docs.
Standard DB API for SQL databases
Generally modules for SQL databases use the Standard Python Database API v2 (defined in PEP249).
API Informations
apilevel �� str: currently '1.0' or '2.0' - '1.0' if undefined threadsafety �� int: level of thread safety
# share module share connections share cursors
no no no
yes no no
yes yes no
yes yes yes
paramstyle �� str: parameter marker for requests
value params example
Question mark style1 ��WHERE name=?
Numeric, positional style1 or 2 ��WHERE name=:1
Named style2 ��WHERE name=:name
ANSI C printf format codes1 ��WHERE name=%s
Python extended format codes2 ��WHERE name=%(name)s
1 Parameters as positional values in a sequence. 2 Parameters as named values in a map.
Warning �� important warning Error �� a catch all InterfaceError �� problem with interface (not database) DatabaseError DataError �� problem with data processing OperationalError �� problem during database operations IntegrityError InternalError ProgrammingError �� SQL programming related error NotSupportedError
Exceptions classes may also be available as Connection objects attributes (optional).
Connection connect(dsn[,user[,password[,host[,database]]]])�� Connection object
(interface defined as a guideline) - dsn=data source name string cx.errorhandler �� fct: (optional) handler for connection errors - errorhandler(connection, cursor/None, errorclass, errorvalue) - default handler fill cx.messages and may raise exceptions cx.messages �� [(exception class,exception value)]: (optional) messages received from database for operations with connection cx.close() ➤ terminate connection (may rollback if not commited) cx.commit() ➤ commit pending transactions cx.rollback() ➤ rollback pending transactions (optionnal) cx.cursor()�� new Cursor object
cu.arraysize �� int: (RW) number of rows to fetch with fetchmany - default to 1 cu.connection �� Connection: (optional) connection used by cursor cu.description �� [(name, type_code, display_size, internal_size, precision, scale, null_ok)]/None: describe result columns cu.errorhandler �� fct: (optional) handler for connection errors - errorhandler(connection, cursor, errorclass, errorvalue) - default handler fill cx.messages and may raise exceptions - inherited from connection cu.lastrowid �� int/None: (optional) row id of last modified column cu.messages �� [(exception class,exception value)]: (optional) messages received from database for operations with cursor cu.rowcount �� int: number of rows produced/affected by last request -
-1 or None if request cant touch rows
cu.rownumber �� int/None: (optional) 0-based index of the cursor in the result set if available cu.callproc(procname[,parameters])�� (parameters) - (optional) call DB stored procedure - in result out and inout parameters may have been replaced by procedure cu.close()ä close the cursor cu.execute(oper[,params]) ➤ prepare and execute DB request - params1 is a sequence or a mapping (see module paramstyle variable) cu.executemany(oper,params_seq) ➤ like execute, with a sequence of params (for multiple values) cu.fetchone()�� (column_value,��) / None: next row of query result, None when no more data available cu.fetchmany([size])�� [(column_value)]: next set of rows of query result, empty list when no more data available - size default to cu.arraysize cu.fetchall()�� [(column_value)]: all remaining rows of query result, empty list when no more data available cu.next()�� (column_value) : (optional) next row of query result, raises
StopIteration when no more data available
cu.nextset() �� True/None: (optional) discards results up to next available set cu.scroll(value[,mode]) ➤ (optional) - scroll cursor in current result set - mode is 'relative' (default) or 'absolute'. cu.setinputsizes(sizes) ➤ predefine memory areas for executeXXX operations parameters - sizes=[param_size,��] - param_size=Type Object or int (max length of a string param) - param_size=None for no predefinition cu.setoutputsize(size[,column]) ➤ set column buffer size for fetches of large columns (e.g. LONGs, BLOBs, etc.) by executeXXX - column is index in result - all columns if column not specified 17a 17b 17c

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cu.__iter__() �� Cursor: (optional) object itself
1 Method __getitem__ is used to get values in params, using
position or name. Can use tuple or dict�� or your own class objects with its __getitem__. If next and __iter__ are defined, cursors are iterable.
DB types Constructors Date(year,month,day)�� object to hold a date value Time(hour,minute,second)�� object to hold a time value Timestamp(year,month,day,hour,minute,second)�� object to hold a
time stamp value
DateFromTicks(ticks)�� object to hold a date value from a given ticks
TimeFromTicks(ticks)�� object to hold a time value from a given ticks
TimestampFromTicks(ticks)�� object to hold a time stamp value from a
given ticks value
Binary(string)�� object to hold a long binary string value
SQL NULL values represented by Python None.
DB types Typecodes
STRING �� string-based column (CHAR) BINARY �� long binary column (LONG, RAW, BLOBs) NUMBER �� numeric column DATETIME �� date/time column ROWID �� row ID column (CHAR)
Batteries included: pdb (Python debugger), code bench with timeit (p10). A must have: pychecker. Take a look: pylint, psyco, pyrex, pycount, trace2html,
depgraph, coverage, pycover, Pyflakes, pyreverse, HAP.
Docs: http://www.python.org/doc/ FAQ Python: http://www.python.org/doc/faq/ PEPs: http://www.python.org/dev/peps/ (Python Enhancement Proposal) HOWTOs: http://www.amk.ca/python/howto/ Cookbook: http://aspn.activestate.com/ASPN/Python/Cookbook/ Dive Into: http://www.diveintopython.org/ 18a 18b 18c ©2005-2007 - Laurent Pointal <laurent.pointal@laposte.net> V0.67 — 2007-4-29 License : Creative Commons [by nc sa]. PQRC at http://laurent.pointal.org/python/pqrc Long Python Quick Reference at http://rgruet.free.fr/ Original Python reference at http://www.python.org/doc
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