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author	Anthony Baxter <anthonybaxter@gmail.com>	2007-04-18 03:35:45 (GMT)
committer	Anthony Baxter <anthonybaxter@gmail.com>	2007-04-18 03:35:45 (GMT)
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\section{Built-in Functions \label{built-in-funcs}} The Python interpreter has a number of functions built into it that are always available. They are listed here in alphabetical order. \setindexsubitem{(built-in function)} \begin{funcdesc}{__import__}{name\optional{, globals\optional{, locals\optional{, fromlist}}}} This function is invoked by the \keyword{import}\stindex{import} statement. It mainly exists so that you can replace it with another function that has a compatible interface, in order to change the semantics of the \keyword{import} statement. For examples of why and how you would do this, see the standard library modules \module{ihooks}\refstmodindex{ihooks} and \refmodule{rexec}\refstmodindex{rexec}. See also the built-in module \refmodule{imp}\refbimodindex{imp}, which defines some useful operations out of which you can build your own \function{__import__()} function. For example, the statement \samp{import spam} results in the following call: \code{__import__('spam',} \code{globals(),} \code{locals(), [])}; the statement \samp{from spam.ham import eggs} results in \samp{__import__('spam.ham', globals(), locals(), ['eggs'])}. Note that even though \code{locals()} and \code{['eggs']} are passed in as arguments, the \function{__import__()} function does not set the local variable named \code{eggs}; this is done by subsequent code that is generated for the import statement. (In fact, the standard implementation does not use its \var{locals} argument at all, and uses its \var{globals} only to determine the package context of the \keyword{import} statement.) When the \var{name} variable is of the form \code{package.module}, normally, the top-level package (the name up till the first dot) is returned, \emph{not} the module named by \var{name}. However, when a non-empty \var{fromlist} argument is given, the module named by \var{name} is returned. This is done for compatibility with the bytecode generated for the different kinds of import statement; when using \samp{import spam.ham.eggs}, the top-level package \module{spam} must be placed in the importing namespace, but when using \samp{from spam.ham import eggs}, the \code{spam.ham} subpackage must be used to find the \code{eggs} variable. As a workaround for this behavior, use \function{getattr()} to extract the desired components. For example, you could define the following helper: \begin{verbatim} def my_import(name): mod = __import__(name) components = name.split('.') for comp in components[1:]: mod = getattr(mod, comp) return mod \end{verbatim} \end{funcdesc} \begin{funcdesc}{abs}{x} Return the absolute value of a number. The argument may be a plain or long integer or a floating point number. If the argument is a complex number, its magnitude is returned. \end{funcdesc} \begin{funcdesc}{basestring}{} This abstract type is the superclass for \class{str} and \class{unicode}. It cannot be called or instantiated, but it can be used to test whether an object is an instance of \class{str} or \class{unicode}. \code{isinstance(obj, basestring)} is equivalent to \code{isinstance(obj, (str, unicode))}. \versionadded{2.3} \end{funcdesc} \begin{funcdesc}{bool}{\optional{x}} Convert a value to a Boolean, using the standard truth testing procedure. If \var{x} is false or omitted, this returns \constant{False}; otherwise it returns \constant{True}. \class{bool} is also a class, which is a subclass of \class{int}. Class \class{bool} cannot be subclassed further. Its only instances are \constant{False} and \constant{True}. \indexii{Boolean}{type} \versionadded{2.2.1} \versionchanged[If no argument is given, this function returns \constant{False}]{2.3} \end{funcdesc} \begin{funcdesc}{callable}{object} Return true if the \var{object} argument appears callable, false if not. If this returns true, it is still possible that a call fails, but if it is false, calling \var{object} will never succeed. Note that classes are callable (calling a class returns a new instance); class instances are callable if they have a \method{__call__()} method. \end{funcdesc} \begin{funcdesc}{chr}{i} Return a string of one character whose \ASCII{} code is the integer \var{i}. For example, \code{chr(97)} returns the string \code{'a'}. This is the inverse of \function{ord()}. The argument must be in the range [0..255], inclusive; \exception{ValueError} will be raised if \var{i} is outside that range. \end{funcdesc} \begin{funcdesc}{classmethod}{function} Return a class method for \var{function}. A class method receives the class as implicit first argument, just like an instance method receives the instance. To declare a class method, use this idiom: \begin{verbatim} class C: @classmethod def f(cls, arg1, arg2, ...): ... \end{verbatim} The \code{@classmethod} form is a function decorator -- see the description of function definitions in chapter 7 of the \citetitle[../ref/ref.html]{Python Reference Manual} for details. It can be called either on the class (such as \code{C.f()}) or on an instance (such as \code{C().f()}). The instance is ignored except for its class. If a class method is called for a derived class, the derived class object is passed as the implied first argument. Class methods are different than \Cpp{} or Java static methods. If you want those, see \function{staticmethod()} in this section. \versionadded{2.2} \versionchanged[Function decorator syntax added]{2.4} \end{funcdesc} \begin{funcdesc}{cmp}{x, y} Compare the two objects \var{x} and \var{y} and return an integer according to the outcome. The return value is negative if \code{\var{x} < \var{y}}, zero if \code{\var{x} == \var{y}} and strictly positive if \code{\var{x} > \var{y}}. \end{funcdesc} \begin{funcdesc}{compile}{string, filename, kind\optional{, flags\optional{, dont_inherit}}} Compile the \var{string} into a code object. Code objects can be executed by an \keyword{exec} statement or evaluated by a call to \function{eval()}. The \var{filename} argument should give the file from which the code was read; pass some recognizable value if it wasn't read from a file (\code{'<string>'} is commonly used). The \var{kind} argument specifies what kind of code must be compiled; it can be \code{'exec'} if \var{string} consists of a sequence of statements, \code{'eval'} if it consists of a single expression, or \code{'single'} if it consists of a single interactive statement (in the latter case, expression statements that evaluate to something else than \code{None} will be printed). When compiling multi-line statements, two caveats apply: line endings must be represented by a single newline character (\code{'\e n'}), and the input must be terminated by at least one newline character. If line endings are represented by \code{'\e r\e n'}, use the string \method{replace()} method to change them into \code{'\e n'}. The optional arguments \var{flags} and \var{dont_inherit} (which are new in Python 2.2) control which future statements (see \pep{236}) affect the compilation of \var{string}. If neither is present (or both are zero) the code is compiled with those future statements that are in effect in the code that is calling compile. If the \var{flags} argument is given and \var{dont_inherit} is not (or is zero) then the future statements specified by the \var{flags} argument are used in addition to those that would be used anyway. If \var{dont_inherit} is a non-zero integer then the \var{flags} argument is it -- the future statements in effect around the call to compile are ignored. Future statemants are specified by bits which can be bitwise or-ed together to specify multiple statements. The bitfield required to specify a given feature can be found as the \member{compiler_flag} attribute on the \class{_Feature} instance in the \module{__future__} module. \end{funcdesc} \begin{funcdesc}{complex}{\optional{real\optional{, imag}}} Create a complex number with the value \var{real} + \var{imag}*j or convert a string or number to a complex number. If the first parameter is a string, it will be interpreted as a complex number and the function must be called without a second parameter. The second parameter can never be a string. Each argument may be any numeric type (including complex). If \var{imag} is omitted, it defaults to zero and the function serves as a numeric conversion function like \function{int()}, \function{long()} and \function{float()}. If both arguments are omitted, returns \code{0j}. \end{funcdesc} \begin{funcdesc}{delattr}{object, name} This is a relative of \function{setattr()}. The arguments are an object and a string. The string must be the name of one of the object's attributes. The function deletes the named attribute, provided the object allows it. For example, \code{delattr(\var{x}, '\var{foobar}')} is equivalent to \code{del \var{x}.\var{foobar}}. \end{funcdesc} \begin{funcdesc}{dict}{\optional{mapping-or-sequence}} Return a new dictionary initialized from an optional positional argument or from a set of keyword arguments. If no arguments are given, return a new empty dictionary. If the positional argument is a mapping object, return a dictionary mapping the same keys to the same values as does the mapping object. Otherwise the positional argument must be a sequence, a container that supports iteration, or an iterator object. The elements of the argument must each also be of one of those kinds, and each must in turn contain exactly two objects. The first is used as a key in the new dictionary, and the second as the key's value. If a given key is seen more than once, the last value associated with it is retained in the new dictionary. If keyword arguments are given, the keywords themselves with their associated values are added as items to the dictionary. If a key is specified both in the positional argument and as a keyword argument, the value associated with the keyword is retained in the dictionary. For example, these all return a dictionary equal to \code{\{"one": 2, "two": 3\}}: \begin{itemize} \item \code{dict(\{'one': 2, 'two': 3\})} \item \code{dict(\{'one': 2, 'two': 3\}.items())} \item \code{dict(\{'one': 2, 'two': 3\}.iteritems())} \item \code{dict(zip(('one', 'two'), (2, 3)))} \item \code{dict([['two', 3], ['one', 2]])} \item \code{dict(one=2, two=3)} \item \code{dict([(['one', 'two'][i-2], i) for i in (2, 3)])} \end{itemize} \versionadded{2.2} \versionchanged[Support for building a dictionary from keyword arguments added]{2.3} \end{funcdesc} \begin{funcdesc}{dir}{\optional{object}} Without arguments, return the list of names in the current local symbol table. With an argument, attempts to return a list of valid attributes for that object. This information is gleaned from the object's \member{__dict__} attribute, if defined, and from the class or type object. The list is not necessarily complete. If the object is a module object, the list contains the names of the module's attributes. If the object is a type or class object, the list contains the names of its attributes, and recursively of the attributes of its bases. Otherwise, the list contains the object's attributes' names, the names of its class's attributes, and recursively of the attributes of its class's base classes. The resulting list is sorted alphabetically. For example: \begin{verbatim} >>> import struct >>> dir() ['__builtins__', '__doc__', '__name__', 'struct'] >>> dir(struct) ['__doc__', '__name__', 'calcsize', 'error', 'pack', 'unpack'] \end{verbatim} \note{Because \function{dir()} is supplied primarily as a convenience for use at an interactive prompt, it tries to supply an interesting set of names more than it tries to supply a rigorously or consistently defined set of names, and its detailed behavior may change across releases.} \end{funcdesc} \begin{funcdesc}{divmod}{a, b} Take two (non complex) numbers as arguments and return a pair of numbers consisting of their quotient and remainder when using long division. With mixed operand types, the rules for binary arithmetic operators apply. For plain and long integers, the result is the same as \code{(\var{a} / \var{b}, \var{a} \%{} \var{b})}. For floating point numbers the result is \code{(\var{q}, \var{a} \%{} \var{b})}, where \var{q} is usually \code{math.floor(\var{a} / \var{b})} but may be 1 less than that. In any case \code{\var{q} * \var{b} + \var{a} \%{} \var{b}} is very close to \var{a}, if \code{\var{a} \%{} \var{b}} is non-zero it has the same sign as \var{b}, and \code{0 <= abs(\var{a} \%{} \var{b}) < abs(\var{b})}. \versionchanged[Using \function{divmod()} with complex numbers is deprecated]{2.3} \end{funcdesc} \begin{funcdesc}{enumerate}{iterable} Return an enumerate object. \var{iterable} must be a sequence, an iterator, or some other object which supports iteration. The \method{next()} method of the iterator returned by \function{enumerate()} returns a tuple containing a count (from zero) and the corresponding value obtained from iterating over \var{iterable}. \function{enumerate()} is useful for obtaining an indexed series: \code{(0, seq[0])}, \code{(1, seq[1])}, \code{(2, seq[2])}, \ldots. \versionadded{2.3} \end{funcdesc} \begin{funcdesc}{eval}{expression\optional{, globals\optional{, locals}}} The arguments are a string and optional globals and locals. If provided, \var{globals} must be a dictionary. If provided, \var{locals} can be any mapping object. \versionchanged[formerly \var{locals} was required to be a dictionary]{2.4} The \var{expression} argument is parsed and evaluated as a Python expression (technically speaking, a condition list) using the \var{globals} and \var{locals} dictionaries as global and local name space. If the \var{globals} dictionary is present and lacks '__builtins__', the current globals are copied into \var{globals} before \var{expression} is parsed. This means that \var{expression} normally has full access to the standard \refmodule[builtin]{__builtin__} module and restricted environments are propagated. If the \var{locals} dictionary is omitted it defaults to the \var{globals} dictionary. If both dictionaries are omitted, the expression is executed in the environment where \keyword{eval} is called. The return value is the result of the evaluated expression. Syntax errors are reported as exceptions. Example: \begin{verbatim} >>> x = 1 >>> print eval('x+1') 2 \end{verbatim} This function can also be used to execute arbitrary code objects (such as those created by \function{compile()}). In this case pass a code object instead of a string. The code object must have been compiled passing \code{'eval'} as the \var{kind} argument. Hints: dynamic execution of statements is supported by the \keyword{exec} statement. Execution of statements from a file is supported by the \function{execfile()} function. The \function{globals()} and \function{locals()} functions returns the current global and local dictionary, respectively, which may be useful to pass around for use by \function{eval()} or \function{execfile()}. \end{funcdesc} \begin{funcdesc}{execfile}{filename\optional{, globals\optional{, locals}}} This function is similar to the \keyword{exec} statement, but parses a file instead of a string. It is different from the \keyword{import} statement in that it does not use the module administration --- it reads the file unconditionally and does not create a new module.\footnote{It is used relatively rarely so does not warrant being made into a statement.} The arguments are a file name and two optional dictionaries. The file is parsed and evaluated as a sequence of Python statements (similarly to a module) using the \var{globals} and \var{locals} dictionaries as global and local namespace. If provided, \var{locals} can be any mapping object. \versionchanged[formerly \var{locals} was required to be a dictionary]{2.4} If the \var{locals} dictionary is omitted it defaults to the \var{globals} dictionary. If both dictionaries are omitted, the expression is executed in the environment where \function{execfile()} is called. The return value is \code{None}. \warning{The default \var{locals} act as described for function \function{locals()} below: modifications to the default \var{locals} dictionary should not be attempted. Pass an explicit \var{locals} dictionary if you need to see effects of the code on \var{locals} after function \function{execfile()} returns. \function{execfile()} cannot be used reliably to modify a function's locals.} \end{funcdesc} \begin{funcdesc}{file}{filename\optional{, mode\optional{, bufsize}}} Return a new file object (described in section~\ref{bltin-file-objects}, ``\ulink{File Objects}{bltin-file-objects.html}''). The first two arguments are the same as for \code{stdio}'s \cfunction{fopen()}: \var{filename} is the file name to be opened, \var{mode} indicates how the file is to be opened: \code{'r'} for reading, \code{'w'} for writing (truncating an existing file), and \code{'a'} opens it for appending (which on \emph{some} \UNIX{} systems means that \emph{all} writes append to the end of the file, regardless of the current seek position). Modes \code{'r+'}, \code{'w+'} and \code{'a+'} open the file for updating (note that \code{'w+'} truncates the file). Append \code{'b'} to the mode to open the file in binary mode, on systems that differentiate between binary and text files (else it is ignored). If the file cannot be opened, \exception{IOError} is raised. In addition to the standard \cfunction{fopen()} values \var{mode} may be \code{'U'} or \code{'rU'}. If Python is built with universal newline support (the default) the file is opened as a text file, but lines may be terminated by any of \code{'\e n'}, the Unix end-of-line convention, \code{'\e r'}, the Macintosh convention or \code{'\e r\e n'}, the Windows convention. All of these external representations are seen as \code{'\e n'} by the Python program. If Python is built without universal newline support \var{mode} \code{'U'} is the same as normal text mode. Note that file objects so opened also have an attribute called \member{newlines} which has a value of \code{None} (if no newlines have yet been seen), \code{'\e n'}, \code{'\e r'}, \code{'\e r\e n'}, or a tuple containing all the newline types seen. If \var{mode} is omitted, it defaults to \code{'r'}. When opening a binary file, you should append \code{'b'} to the \var{mode} value for improved portability. (It's useful even on systems which don't treat binary and text files differently, where it serves as documentation.) \index{line-buffered I/O}\index{unbuffered I/O}\index{buffer size, I/O} \index{I/O control!buffering} The optional \var{bufsize} argument specifies the file's desired buffer size: 0 means unbuffered, 1 means line buffered, any other positive value means use a buffer of (approximately) that size. A negative \var{bufsize} means to use the system default, which is usually line buffered for tty devices and fully buffered for other files. If omitted, the system default is used.\footnote{ Specifying a buffer size currently has no effect on systems that don't have \cfunction{setvbuf()}. The interface to specify the buffer size is not done using a method that calls \cfunction{setvbuf()}, because that may dump core when called after any I/O has been performed, and there's no reliable way to determine whether this is the case.} The \function{file()} constructor is new in Python 2.2. The previous spelling, \function{open()}, is retained for compatibility, and is an alias for \function{file()}. \end{funcdesc} \begin{funcdesc}{filter}{function, list} Construct a list from those elements of \var{list} for which \var{function} returns true. \var{list} may be either a sequence, a container which supports iteration, or an iterator, If \var{list} is a string or a tuple, the result also has that type; otherwise it is always a list. If \var{function} is \code{None}, the identity function is assumed, that is, all elements of \var{list} that are false (zero or empty) are removed. Note that \code{filter(function, \var{list})} is equivalent to \code{[item for item in \var{list} if function(item)]} if function is not \code{None} and \code{[item for item in \var{list} if item]} if function is \code{None}. \end{funcdesc} \begin{funcdesc}{float}{\optional{x}} Convert a string or a number to floating point. If the argument is a string, it must contain a possibly signed decimal or floating point number, possibly embedded in whitespace. Otherwise, the argument may be a plain or long integer or a floating point number, and a floating point number with the same value (within Python's floating point precision) is returned. If no argument is given, returns \code{0.0}. \note{When passing in a string, values for NaN\index{NaN} and Infinity\index{Infinity} may be returned, depending on the underlying C library. The specific set of strings accepted which cause these values to be returned depends entirely on the C library and is known to vary.} \end{funcdesc} \begin{funcdesc}{frozenset}{\optional{iterable}} Return a frozenset object whose elements are taken from \var{iterable}. Frozensets are sets that have no update methods but can be hashed and used as members of other sets or as dictionary keys. The elements of a frozenset must be immutable themselves. To represent sets of sets, the inner sets should also be \class{frozenset} objects. If \var{iterable} is not specified, returns a new empty set, \code{frozenset([])}. \versionadded{2.4} \end{funcdesc} \begin{funcdesc}{getattr}{object, name\optional{, default}} Return the value of the named attributed of \var{object}. \var{name} must be a string. If the string is the name of one of the object's attributes, the result is the value of that attribute. For example, \code{getattr(x, 'foobar')} is equivalent to \code{x.foobar}. If the named attribute does not exist, \var{default} is returned if provided, otherwise \exception{AttributeError} is raised. \end{funcdesc} \begin{funcdesc}{globals}{} Return a dictionary representing the current global symbol table. This is always the dictionary of the current module (inside a function or method, this is the module where it is defined, not the module from which it is called). \end{funcdesc} \begin{funcdesc}{hasattr}{object, name} The arguments are an object and a string. The result is \code{True} if the string is the name of one of the object's attributes, \code{False} if not. (This is implemented by calling \code{getattr(\var{object}, \var{name})} and seeing whether it raises an exception or not.) \end{funcdesc} \begin{funcdesc}{hash}{object} Return the hash value of the object (if it has one). Hash values are integers. They are used to quickly compare dictionary keys during a dictionary lookup. Numeric values that compare equal have the same hash value (even if they are of different types, as is the case for 1 and 1.0). \end{funcdesc} \begin{funcdesc}{help}{\optional{object}} Invoke the built-in help system. (This function is intended for interactive use.) If no argument is given, the interactive help system starts on the interpreter console. If the argument is a string, then the string is looked up as the name of a module, function, class, method, keyword, or documentation topic, and a help page is printed on the console. If the argument is any other kind of object, a help page on the object is generated. \versionadded{2.2} \end{funcdesc} \begin{funcdesc}{hex}{x} Convert an integer number (of any size) to a hexadecimal string. The result is a valid Python expression. \versionchanged[Formerly only returned an unsigned literal.]{2.4} \end{funcdesc} \begin{funcdesc}{id}{object} Return the ``identity'' of an object. This is an integer (or long integer) which is guaranteed to be unique and constant for this object during its lifetime. Two objects with non-overlapping lifetimes may have the same \function{id()} value. (Implementation note: this is the address of the object.) \end{funcdesc} \begin{funcdesc}{input}{\optional{prompt}} Equivalent to \code{eval(raw_input(\var{prompt}))}. \warning{This function is not safe from user errors! It expects a valid Python expression as input; if the input is not syntactically valid, a \exception{SyntaxError} will be raised. Other exceptions may be raised if there is an error during evaluation. (On the other hand, sometimes this is exactly what you need when writing a quick script for expert use.)} If the \refmodule{readline} module was loaded, then \function{input()} will use it to provide elaborate line editing and history features. Consider using the \function{raw_input()} function for general input from users. \end{funcdesc} \begin{funcdesc}{int}{\optional{x\optional{, radix}}} Convert a string or number to a plain integer. If the argument is a string, it must contain a possibly signed decimal number representable as a Python integer, possibly embedded in whitespace. The \var{radix} parameter gives the base for the conversion and may be any integer in the range [2, 36], or zero. If \var{radix} is zero, the proper radix is guessed based on the contents of string; the interpretation is the same as for integer literals. If \var{radix} is specified and \var{x} is not a string, \exception{TypeError} is raised. Otherwise, the argument may be a plain or long integer or a floating point number. Conversion of floating point numbers to integers truncates (towards zero). If the argument is outside the integer range a long object will be returned instead. If no arguments are given, returns \code{0}. \end{funcdesc} \begin{funcdesc}{isinstance}{object, classinfo} Return true if the \var{object} argument is an instance of the \var{classinfo} argument, or of a (direct or indirect) subclass thereof. Also return true if \var{classinfo} is a type object and \var{object} is an object of that type. If \var{object} is not a class instance or an object of the given type, the function always returns false. If \var{classinfo} is neither a class object nor a type object, it may be a tuple of class or type objects, or may recursively contain other such tuples (other sequence types are not accepted). If \var{classinfo} is not a class, type, or tuple of classes, types, and such tuples, a \exception{TypeError} exception is raised. \versionchanged[Support for a tuple of type information was added]{2.2} \end{funcdesc} \begin{funcdesc}{issubclass}{class, classinfo} Return true if \var{class} is a subclass (direct or indirect) of \var{classinfo}. A class is considered a subclass of itself. \var{classinfo} may be a tuple of class objects, in which case every entry in \var{classinfo} will be checked. In any other case, a \exception{TypeError} exception is raised. \versionchanged[Support for a tuple of type information was added]{2.3} \end{funcdesc} \begin{funcdesc}{iter}{o\optional{, sentinel}} Return an iterator object. The first argument is interpreted very differently depending on the presence of the second argument. Without a second argument, \var{o} must be a collection object which supports the iteration protocol (the \method{__iter__()} method), or it must support the sequence protocol (the \method{__getitem__()} method with integer arguments starting at \code{0}). If it does not support either of those protocols, \exception{TypeError} is raised. If the second argument, \var{sentinel}, is given, then \var{o} must be a callable object. The iterator created in this case will call \var{o} with no arguments for each call to its \method{next()} method; if the value returned is equal to \var{sentinel}, \exception{StopIteration} will be raised, otherwise the value will be returned. \versionadded{2.2} \end{funcdesc} \begin{funcdesc}{len}{s} Return the length (the number of items) of an object. The argument may be a sequence (string, tuple or list) or a mapping (dictionary). \end{funcdesc} \begin{funcdesc}{list}{\optional{sequence}} Return a list whose items are the same and in the same order as \var{sequence}'s items. \var{sequence} may be either a sequence, a container that supports iteration, or an iterator object. If \var{sequence} is already a list, a copy is made and returned, similar to \code{\var{sequence}[:]}. For instance, \code{list('abc')} returns \code{['a', 'b', 'c']} and \code{list( (1, 2, 3) )} returns \code{[1, 2, 3]}. If no argument is given, returns a new empty list, \code{[]}. \end{funcdesc} \begin{funcdesc}{locals}{} Update and return a dictionary representing the current local symbol table. \warning{The contents of this dictionary should not be modified; changes may not affect the values of local variables used by the interpreter.} \end{funcdesc} \begin{funcdesc}{long}{\optional{x\optional{, radix}}} Convert a string or number to a long integer. If the argument is a string, it must contain a possibly signed number of arbitrary size, possibly embedded in whitespace. The \var{radix} argument is interpreted in the same way as for \function{int()}, and may only be given when \var{x} is a string. Otherwise, the argument may be a plain or long integer or a floating point number, and a long integer with the same value is returned. Conversion of floating point numbers to integers truncates (towards zero). If no arguments are given, returns \code{0L}. \end{funcdesc} \begin{funcdesc}{map}{function, list, ...} Apply \var{function} to every item of \var{list} and return a list of the results. If additional \var{list} arguments are passed, \var{function} must take that many arguments and is applied to the items of all lists in parallel; if a list is shorter than another it is assumed to be extended with \code{None} items. If \var{function} is \code{None}, the identity function is assumed; if there are multiple list arguments, \function{map()} returns a list consisting of tuples containing the corresponding items from all lists (a kind of transpose operation). The \var{list} arguments may be any kind of sequence; the result is always a list. \end{funcdesc} \begin{funcdesc}{max}{s\optional{, args...}\optional{key}} With a single argument \var{s}, return the largest item of a non-empty sequence (such as a string, tuple or list). With more than one argument, return the largest of the arguments. The optional \var{key} argument specifies a one-argument ordering function like that used for \method{list.sort()}. The \var{key} argument, if supplied, must be in keyword form (for example, \samp{max(a,b,c,key=func)}). \versionchanged[Added support for the optional \var{key} argument]{2.5} \end{funcdesc} \begin{funcdesc}{min}{s\optional{, args...}} With a single argument \var{s}, return the smallest item of a non-empty sequence (such as a string, tuple or list). With more than one argument, return the smallest of the arguments. The optional \var{key} argument specifies a one-argument ordering function like that used for \method{list.sort()}. The \var{key} argument, if supplied, must be in keyword form (for example, \samp{min(a,b,c,key=func)}). \versionchanged[Added support for the optional \var{key} argument]{2.5} \end{funcdesc} \begin{funcdesc}{object}{} Return a new featureless object. \function{object()} is a base for all new style classes. It has the methods that are common to all instances of new style classes. \versionadded{2.2} \versionchanged[This function does not accept any arguments. Formerly, it accepted arguments but ignored them]{2.3} \end{funcdesc} \begin{funcdesc}{oct}{x} Convert an integer number (of any size) to an octal string. The result is a valid Python expression. \versionchanged[Formerly only returned an unsigned literal.]{2.4} \end{funcdesc} \begin{funcdesc}{open}{filename\optional{, mode\optional{, bufsize}}} An alias for the \function{file()} function above. \end{funcdesc} \begin{funcdesc}{ord}{c} Return the \ASCII{} value of a string of one character or a Unicode character. E.g., \code{ord('a')} returns the integer \code{97}, \code{ord(u'\e u2020')} returns \code{8224}. This is the inverse of \function{chr()} for strings and of \function{unichr()} for Unicode characters. \end{funcdesc} \begin{funcdesc}{pow}{x, y\optional{, z}} Return \var{x} to the power \var{y}; if \var{z} is present, return \var{x} to the power \var{y}, modulo \var{z} (computed more efficiently than \code{pow(\var{x}, \var{y}) \%\ \var{z}}). The arguments must have numeric types. With mixed operand types, the coercion rules for binary arithmetic operators apply. For int and long int operands, the result has the same type as the operands (after coercion) unless the second argument is negative; in that case, all arguments are converted to float and a float result is delivered. For example, \code{10**2} returns \code{100}, but \code{10**-2} returns \code{0.01}. (This last feature was added in Python 2.2. In Python 2.1 and before, if both arguments were of integer types and the second argument was negative, an exception was raised.) If the second argument is negative, the third argument must be omitted. If \var{z} is present, \var{x} and \var{y} must be of integer types, and \var{y} must be non-negative. (This restriction was added in Python 2.2. In Python 2.1 and before, floating 3-argument \code{pow()} returned platform-dependent results depending on floating-point rounding accidents.) \end{funcdesc} \begin{funcdesc}{property}{\optional{fget\optional{, fset\optional{, fdel\optional{, doc}}}}} Return a property attribute for new-style classes (classes that derive from \class{object}). \var{fget} is a function for getting an attribute value, likewise \var{fset} is a function for setting, and \var{fdel} a function for del'ing, an attribute. Typical use is to define a managed attribute x: \begin{verbatim} class C(object): def getx(self): return self.__x def setx(self, value): self.__x = value def delx(self): del self.__x x = property(getx, setx, delx, "I'm the 'x' property.") \end{verbatim} \versionadded{2.2} \end{funcdesc} \begin{funcdesc}{range}{\optional{start,} stop\optional{, step}} This is a versatile function to create lists containing arithmetic progressions. It is most often used in \keyword{for} loops. The arguments must be plain integers. If the \var{step} argument is omitted, it defaults to \code{1}. If the \var{start} argument is omitted, it defaults to \code{0}. The full form returns a list of plain integers \code{[\var{start}, \var{start} + \var{step}, \var{start} + 2 * \var{step}, \ldots]}. If \var{step} is positive, the last element is the largest \code{\var{start} + \var{i} * \var{step}} less than \var{stop}; if \var{step} is negative, the last element is the largest \code{\var{start} + \var{i} * \var{step}} greater than \var{stop}. \var{step} must not be zero (or else \exception{ValueError} is raised). Example: \begin{verbatim} >>> range(10) [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] >>> range(1, 11) [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] >>> range(0, 30, 5) [0, 5, 10, 15, 20, 25] >>> range(0, 10, 3) [0, 3, 6, 9] >>> range(0, -10, -1) [0, -1, -2, -3, -4, -5, -6, -7, -8, -9] >>> range(0) [] >>> range(1, 0) [] \end{verbatim} \end{funcdesc} \begin{funcdesc}{raw_input}{\optional{prompt}} If the \var{prompt} argument is present, it is written to standard output without a trailing newline. The function then reads a line from input, converts it to a string (stripping a trailing newline), and returns that. When \EOF{} is read, \exception{EOFError} is raised. Example: \begin{verbatim} >>> s = raw_input('--> ') --> Monty Python's Flying Circus >>> s "Monty Python's Flying Circus" \end{verbatim} If the \refmodule{readline} module was loaded, then \function{raw_input()} will use it to provide elaborate line editing and history features. \end{funcdesc} \begin{funcdesc}{reduce}{function, sequence\optional{, initializer}} Apply \var{function} of two arguments cumulatively to the items of \var{sequence}, from left to right, so as to reduce the sequence to a single value. For example, \code{reduce(lambda x, y: x+y, [1, 2, 3, 4, 5])} calculates \code{((((1+2)+3)+4)+5)}. The left argument, \var{x}, is the accumulated value and the right argument, \var{y}, is the update value from the \var{sequence}. If the optional \var{initializer} is present, it is placed before the items of the sequence in the calculation, and serves as a default when the sequence is empty. If \var{initializer} is not given and \var{sequence} contains only one item, the first item is returned. \end{funcdesc} \begin{funcdesc}{reload}{module} Reload a previously imported \var{module}. The argument must be a module object, so it must have been successfully imported before. This is useful if you have edited the module source file using an external editor and want to try out the new version without leaving the Python interpreter. The return value is the module object (the same as the \var{module} argument). When \code{reload(module)} is executed: \begin{itemize} \item Python modules' code is recompiled and the module-level code reexecuted, defining a new set of objects which are bound to names in the module's dictionary. The \code{init} function of extension modules is not called a second time. \item As with all other objects in Python the old objects are only reclaimed after their reference counts drop to zero. \item The names in the module namespace are updated to point to any new or changed objects. \item Other references to the old objects (such as names external to the module) are not rebound to refer to the new objects and must be updated in each namespace where they occur if that is desired. \end{itemize}


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