| \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\optional{, level}}}}} |
| 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(), [], -1)}; the statement \samp{from spam.ham import eggs} |
| results in \samp{__import__('spam.ham', globals(), locals(), |
| ['eggs'], -1)}. 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} |
| |
| \var{level} specifies whether to use absolute or relative imports. |
| The default is \code{-1} which indicates both absolute and relative |
| imports will be attempted. \code{0} means only perform absolute imports. |
| Positive values for \var{level} indicate the number of parent directories |
| to search relative to the directory of the module calling |
| \function{__import__}. |
| \versionchanged[The level parameter was added]{2.5} |
| \versionchanged[Keyword support for parameters was added]{2.5} |
| \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}{all}{iterable} |
| Return True if all elements of the \var{iterable} are true. |
| Equivalent to: |
| \begin{verbatim} |
| def all(iterable): |
| for element in iterable: |
| if not element: |
| return False |
| return True |
| \end{verbatim} |
| \versionadded{2.5} |
| \end{funcdesc} |
| |
| \begin{funcdesc}{any}{iterable} |
| Return True if any element of the \var{iterable} is true. |
| Equivalent to: |
| \begin{verbatim} |
| def any(iterable): |
| for element in iterable: |
| if element: |
| return True |
| return False |
| \end{verbatim} |
| \versionadded{2.5} |
| \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. |
| |
| For more information on class methods, consult the documentation on the |
| standard type hierarchy in chapter 3 of the |
| \citetitle[../ref/types.html]{Python Reference Manual} (at the bottom). |
| \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 a call to \function{exec()} 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 statements 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{arg}} |
| 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 \var{arg} 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 |
| \function{exec()} function. 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}{exec}{object\optional{, globals\optional{, locals}}} |
| This function supports dynamic execution of Python code. |
| \var{object} must be either a string, an open file object, or |
| a code object. If it is a string, the string is parsed as a suite of |
| Python statements which is then executed (unless a syntax error |
| occurs). If it is an open file, the file is parsed until \EOF{} and |
| executed. If it is a code object, it is simply executed. In all |
| cases, the code that's executed is expected to be valid as file |
| input (see the section ``File input'' in the Reference Manual). |
| Be aware that the \keyword{return} and \keyword{yield} statements may |
| not be used outside of function definitions even within the context of |
| code passed to the \function{exec()} function. |
| The return value is \code{None}. |
| |
| In all cases, if the optional parts are omitted, the code is executed |
| in the current scope. If only \var{globals} is provided, it must be |
| a dictionary, which will be used for both the global and the local |
| variables. If \var{globals} and \var{locals} are given, they are used |
| for the global and local variables, respectively. If provided, |
| \var{locals} can be any mapping object. |
| |
| If the \var{globals} dictionary does not contain a value for the |
| key \code{__builtins__}, a reference to the dictionary of the built-in |
| module \module{__builtin__} is inserted under that key. That way you |
| can control what builtins are available to the executed code by |
| inserting your own \code{__builtins__} dictionary into \var{globals} |
| before passing it to \function{exec()}. |
| |
| \note{The built-in functions \function{globals()} and \function{locals()} |
| return the current global and local dictionary, respectively, which |
| may be useful to pass around for use as the second and third |
| argument to \function{exec()}.} |
| \end{funcdesc} |
| |
| \begin{funcdesc}{execfile}{filename\optional{, globals\optional{, locals}}} |
| This function is similar to the \function{exec()} function, but parses a |
| file given by the file name 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. |
| |
| 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}}} |
| Constructor function for the \class{file} type, described further |
| in section~\ref{bltin-file-objects}, ``\ulink{File |
| Objects}{bltin-file-objects.html}''. The constructor's arguments |
| are the same as those of the \function{open()} built-in function |
| described below. |
| |
| When opening a file, it's preferable to use \function{open()} instead of |
| invoking this constructor directly. \class{file} is more suited to |
| type testing (for example, writing \samp{isinstance(f, file)}). |
| |
| \versionadded{2.2} |
| \end{funcdesc} |
| |
| \begin{funcdesc}{filter}{function, iterable} |
| Construct a list from those elements of \var{iterable} for which |
| \var{function} returns true. \var{iterable} may be either a sequence, a |
| container which supports iteration, or an iterator, If \var{iterable} |
| 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{iterable} that are false are removed. |
| |
| Note that \code{filter(function, \var{iterable})} is equivalent to |
| \code{[item for item in \var{iterable} if function(item)]} if function is |
| not \code{None} and \code{[item for item in \var{iterable} 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}{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{iterable}} |
| Return a list whose items are the same and in the same order as |
| \var{iterable}'s items. \var{iterable} may be either a sequence, a |
| container that supports iteration, or an iterator object. If |
| \var{iterable} is already a list, a copy is made and returned, |
| similar to \code{\var{iterable}[:]}. 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, iterable, ...} |
| Apply \var{function} to every item of \var{iterable} and return a list |
| of the results. If additional \var{iterable} arguments are passed, |
| \var{function} must take that many arguments and is applied to the |
| items from all iterables in parallel. If one iterable 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 arguments, \function{map()} returns a list consisting |
| of tuples containing the corresponding items from all iterables (a kind |
| of transpose operation). The \var{iterable} arguments may be a sequence |
| or any iterable object; the result is always a list. |
| \end{funcdesc} |
| |
| \begin{funcdesc}{max}{iterable\optional{, args...}\optional{key}} |
| With a single argument \var{iterable}, return the largest item of a |
| non-empty iterable (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}{iterable\optional{, args...}\optional{key}} |
| With a single argument \var{iterable}, return the smallest item of a |
| non-empty iterable (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. \class{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}}} |
| Open a file, returning an object of the \class{file} type described |
| in section~\ref{bltin-file-objects}, ``\ulink{File |
| Objects}{bltin-file-objects.html}''. If the file cannot be opened, |
| \exception{IOError} is raised. When opening a file, it's |
| preferable to use \function{open()} instead of invoking the |
| \class{file} constructor directly. |
| |
| The first two arguments are the same as for \code{stdio}'s |
| \cfunction{fopen()}: \var{filename} is the file name to be opened, |
| and \var{mode} is a string indicating how the file is to be opened. |
| |
| The most commonly-used values of \var{mode} are \code{'r'} for |
| reading, \code{'w'} for writing (truncating the file if it already |
| exists), and \code{'a'} 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). 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 to open the file in binary |
| mode, which will improve portability. (Appending \code{'b'} is |
| useful even on systems that don't treat binary and text files |
| differently, where it serves as documentation.) See below for more |
| possible values of \var{mode}. |
| |
| \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.} |
| |
| 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; on systems |
| that don't have this distinction, adding the \code{'b'} has no effect. |
| |
| In addition to the standard \cfunction{fopen()} values \var{mode} |
| may be \code{'U'} or \code{'rU'}. Python is usually built with universal |
| newline support; supplying \code{'U'} opens the file as a text file, but |
| lines may be terminated by any of the following: the \UNIX{} end-of-line |
| convention \code{'\e n'}, |
| the Macintosh convention \code{'\e r'}, or the Windows |
| convention \code{'\e r\e n'}. All of these external representations are seen as |
| \code{'\e n'} |
| by the Python program. If Python is built without universal newline support |
| a \var{mode} with \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. |
| |
| Python enforces that the mode, after stripping \code{'U'}, begins with |
| \code{'r'}, \code{'w'} or \code{'a'}. |
| |
| \versionchanged[Restriction on first letter of mode string |
| introduced]{2.5} |
| \end{funcdesc} |
| |
| \begin{funcdesc}{ord}{c} |
| Given a string of length one, return an integer representing the |
| Unicode code point of the character when the argument is a unicode object, |
| or the value of the byte when the argument is an 8-bit string. |
| For example, \code{ord('a')} returns the integer \code{97}, |
| \code{ord(u'\e u2020')} returns \code{8224}. This is the inverse of |
| \function{chr()} for 8-bit strings and of \function{unichr()} for unicode |
| objects. If a unicode argument is given and Python was built with |
| UCS2 Unicode, then the character's code point must be in the range |
| [0..65535] inclusive; otherwise the string length is two, and a |
| \exception{TypeError} will be raised. |
| \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 two-argument form \code{pow(\var{x}, \var{y})} is equivalent to using |
| the power operator: \code{\var{x}**\var{y}}. |
| |
| 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 __init__(self): self._x = None |
| 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} |
| |
| If given, \var{doc} will be the docstring of the property attribute. |
| Otherwise, the property will copy \var{fget}'s docstring (if it |
| exists). This makes it possible to create read-only properties |
| easily using \function{property()} as a decorator: |
| |
| \begin{verbatim} |
| class Parrot(object): |
| def __init__(self): |
| self._voltage = 100000 |
| |
| @property |
| def voltage(self): |
| """Get the current voltage.""" |
| return self._voltage |
| \end{verbatim} |
| |
| turns the \method{voltage()} method into a ``getter'' for a read-only |
| attribute with the same name. |
| |
| \versionadded{2.2} |
| \versionchanged[Use \var{fget}'s docstring if no \var{doc} given]{2.5} |
| \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 smallest \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}{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} |
| |
| There are a number of other caveats: |
| |
| If a module is syntactically correct but its initialization fails, |
| the first \keyword{import} statement for it does not bind its name |
| locally, but does store a (partially initialized) module object in |
| \code{sys.modules}. To reload the module you must first |
| \keyword{import} it again (this will bind the name to the partially |
| initialized module object) before you can \function{reload()} it. |
| |
| When a module is reloaded, its dictionary (containing the module's |
| global variables) is retained. Redefinitions of names will override |
| the old definitions, so this is generally not a problem. If the new |
| version of a module does not define a name that was defined by the |
| old version, the old definition remains. This feature can be used |
| to the module's advantage if it maintains a global table or cache of |
| objects --- with a \keyword{try} statement it can test for the |
| table's presence and skip its initialization if desired: |
| |
| \begin{verbatim} |
| try: |
| cache |
| except NameError: |
| cache = {} |
| \end{verbatim} |
| |
| |
| It is legal though generally not very useful to reload built-in or |
| dynamically loaded modules, except for \refmodule{sys}, |
| \refmodule[main]{__main__} and \refmodule[builtin]{__builtin__}. In |
| many cases, however, extension modules are not designed to be |
| initialized more than once, and may fail in arbitrary ways when |
| reloaded. |
| |
| If a module imports objects from another module using \keyword{from} |
| \ldots{} \keyword{import} \ldots{}, calling \function{reload()} for |
| the other module does not redefine the objects imported from it --- |
| one way around this is to re-execute the \keyword{from} statement, |
| another is to use \keyword{import} and qualified names |
| (\var{module}.\var{name}) instead. |
| |
| If a module instantiates instances of a class, reloading the module |
| that defines the class does not affect the method definitions of the |
| instances --- they continue to use the old class definition. The |
| same is true for derived classes. |
| \end{funcdesc} |
| |
| \begin{funcdesc}{repr}{object} |
| Return a string containing a printable representation of an object. |
| This is the same value yielded by conversions (reverse quotes). |
| It is sometimes useful to be able to access this operation as an |
| ordinary function. For many types, this function makes an attempt |
| to return a string that would yield an object with the same value |
| when passed to \function{eval()}. |
| \end{funcdesc} |
| |
| \begin{funcdesc}{reversed}{seq} |
| Return a reverse iterator. \var{seq} must be an object which |
| supports the sequence protocol (the __len__() method and the |
| \method{__getitem__()} method with integer arguments starting at |
| \code{0}). |
| \versionadded{2.4} |
| \end{funcdesc} |
| |
| \begin{funcdesc}{round}{x\optional{, n}} |
| Return the floating point value \var{x} rounded to \var{n} digits |
| after the decimal point. If \var{n} is omitted, it defaults to zero. |
| The result is a floating point number. Values are rounded to the |
| closest multiple of 10 to the power minus \var{n}; if two multiples |
| are equally close, rounding is done away from 0 (so. for example, |
| \code{round(0.5)} is \code{1.0} and \code{round(-0.5)} is \code{-1.0}). |
| \end{funcdesc} |
| |
| \begin{funcdesc}{set}{\optional{iterable}} |
| Return a set whose elements are taken from \var{iterable}. The elements |
| must be immutable. To represent sets of sets, the inner sets should |
| be \class{frozenset} objects. If \var{iterable} is not specified, |
| returns a new empty set, \code{set([])}. |
| \versionadded{2.4} |
| \end{funcdesc} |
| |
| \begin{funcdesc}{setattr}{object, name, value} |
| This is the counterpart of \function{getattr()}. The arguments are an |
| object, a string and an arbitrary value. The string may name an |
| existing attribute or a new attribute. The function assigns the |
| value to the attribute, provided the object allows it. For example, |
| \code{setattr(\var{x}, '\var{foobar}', 123)} is equivalent to |
| \code{\var{x}.\var{foobar} = 123}. |
| \end{funcdesc} |
| |
| \begin{funcdesc}{slice}{\optional{start,} stop\optional{, step}} |
| Return a slice object representing the set of indices specified by |
| \code{range(\var{start}, \var{stop}, \var{step})}. The \var{start} |
| and \var{step} arguments default to \code{None}. Slice objects have |
| read-only data attributes \member{start}, \member{stop} and |
| \member{step} which merely return the argument values (or their |
| default). They have no other explicit functionality; however they |
| are used by Numerical Python\index{Numerical Python} and other third |
| party extensions. Slice objects are also generated when extended |
| indexing syntax is used. For example: \samp{a[start:stop:step]} or |
| \samp{a[start:stop, i]}. |
| \end{funcdesc} |
| |
| \begin{funcdesc}{sorted}{iterable\optional{, cmp\optional{, |
| key\optional{, reverse}}}} |
| Return a new sorted list from the items in \var{iterable}. |
| |
| The optional arguments \var{cmp}, \var{key}, and \var{reverse} have |
| the same meaning as those for the \method{list.sort()} method |
| (described in section~\ref{typesseq-mutable}). |
| |
| \var{cmp} specifies a custom comparison function of two arguments |
| (iterable elements) which should return a negative, zero or positive |
| number depending on whether the first argument is considered smaller |
| than, equal to, or larger than the second argument: |
| \samp{\var{cmp}=\keyword{lambda} \var{x},\var{y}: |
| \function{cmp}(x.lower(), y.lower())} |
| |
| \var{key} specifies a function of one argument that is used to |
| extract a comparison key from each list element: |
| \samp{\var{key}=\function{str.lower}} |
| |
| \var{reverse} is a boolean value. If set to \code{True}, then the |
| list elements are sorted as if each comparison were reversed. |
| |
| In general, the \var{key} and \var{reverse} conversion processes are |
| much faster than specifying an equivalent \var{cmp} function. This is |
| because \var{cmp} is called multiple times for each list element while |
| \var{key} and \var{reverse} touch each element only once. |
| |
| \versionadded{2.4} |
| \end{funcdesc} |
| |
| \begin{funcdesc}{staticmethod}{function} |
| Return a static method for \var{function}. |
| |
| A static method does not receive an implicit first argument. |
| To declare a static method, use this idiom: |
| |
| \begin{verbatim} |
| class C: |
| @staticmethod |
| def f(arg1, arg2, ...): ... |
| \end{verbatim} |
| |
| The \code{@staticmethod} form is a function decorator -- see the description |
| of function definitions in chapter 7 of the |
| \citetitle[../ref/function.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. |
| |
| Static methods in Python are similar to those found in Java or \Cpp. |
| For a more advanced concept, see \function{classmethod()} in this |
| section. |
| |
| For more information on static methods, consult the documentation on the |
| standard type hierarchy in chapter 3 of the |
| \citetitle[../ref/types.html]{Python Reference Manual} (at the bottom). |
| \versionadded{2.2} |
| \versionchanged[Function decorator syntax added]{2.4} |
| \end{funcdesc} |
| |
| \begin{funcdesc}{str}{\optional{object}} |
| Return a string containing a nicely printable representation of an |
| object. For strings, this returns the string itself. The |
| difference with \code{repr(\var{object})} is that |
| \code{str(\var{object})} does not always attempt to return a string |
| that is acceptable to \function{eval()}; its goal is to return a |
| printable string. If no argument is given, returns the empty |
| string, \code{''}. |
| \end{funcdesc} |
| |
| \begin{funcdesc}{sum}{iterable\optional{, start}} |
| Sums \var{start} and the items of an \var{iterable} from left to |
| right and returns the total. \var{start} defaults to \code{0}. |
| The \var{iterable}'s items are normally numbers, and are not allowed |
| to be strings. The fast, correct way to concatenate a sequence of |
| strings is by calling \code{''.join(\var{sequence})}. |
| \versionadded{2.3} |
| \end{funcdesc} |
| |
| \begin{funcdesc}{super}{type\optional{, object-or-type}} |
| Return the superclass of \var{type}. If the second argument is omitted |
| the super object returned is unbound. If the second argument is an |
| object, \code{isinstance(\var{obj}, \var{type})} must be true. If |
| the second argument is a type, \code{issubclass(\var{type2}, |
| \var{type})} must be true. |
| \function{super()} only works for new-style classes. |
| |
| A typical use for calling a cooperative superclass method is: |
| \begin{verbatim} |
| class C(B): |
| def meth(self, arg): |
| super(C, self).meth(arg) |
| \end{verbatim} |
| |
| Note that \function{super} is implemented as part of the binding process for |
| explicit dotted attribute lookups such as |
| \samp{super(C, self).__getitem__(name)}. Accordingly, \function{super} is |
| undefined for implicit lookups using statements or operators such as |
| \samp{super(C, self)[name]}. |
| \versionadded{2.2} |
| \end{funcdesc} |
| |
| \begin{funcdesc}{tuple}{\optional{iterable}} |
| Return a tuple whose items are the same and in the same order as |
| \var{iterable}'s items. \var{iterable} may be a sequence, a |
| container that supports iteration, or an iterator object. |
| If \var{iterable} is already a tuple, it |
| is returned unchanged. For instance, \code{tuple('abc')} returns |
| \code{('a', 'b', 'c')} and \code{tuple([1, 2, 3])} returns |
| \code{(1, 2, 3)}. If no argument is given, returns a new empty |
| tuple, \code{()}. |
| \end{funcdesc} |
| |
| \begin{funcdesc}{type}{object} |
| Return the type of an \var{object}. The return value is a |
| type\obindex{type} object. The \function{isinstance()} built-in |
| function is recommended for testing the type of an object. |
| |
| With three arguments, \function{type} functions as a constructor |
| as detailed below. |
| \end{funcdesc} |
| |
| \begin{funcdesc}{type}{name, bases, dict} |
| Return a new type object. This is essentially a dynamic form of the |
| \keyword{class} statement. The \var{name} string is the class name |
| and becomes the \member{__name__} attribute; the \var{bases} tuple |
| itemizes the base classes and becomes the \member{__bases__} |
| attribute; and the \var{dict} dictionary is the namespace containing |
| definitions for class body and becomes the \member{__dict__} |
| attribute. For example, the following two statements create |
| identical \class{type} objects: |
| |
| \begin{verbatim} |
| >>> class X(object): |
| ... a = 1 |
| ... |
| >>> X = type('X', (object,), dict(a=1)) |
| \end{verbatim} |
| \versionadded{2.2} |
| \end{funcdesc} |
| |
| \begin{funcdesc}{unichr}{i} |
| Return the Unicode string of one character whose Unicode code is the |
| integer \var{i}. For example, \code{unichr(97)} returns the string |
| \code{u'a'}. This is the inverse of \function{ord()} for Unicode |
| strings. The valid range for the argument depends how Python was |
| configured -- it may be either UCS2 [0..0xFFFF] or UCS4 [0..0x10FFFF]. |
| \exception{ValueError} is raised otherwise. |
| \versionadded{2.0} |
| \end{funcdesc} |
| |
| \begin{funcdesc}{unicode}{\optional{object\optional{, encoding |
| \optional{, errors}}}} |
| Return the Unicode string version of \var{object} using one of the |
| following modes: |
| |
| If \var{encoding} and/or \var{errors} are given, \code{unicode()} |
| will decode the object which can either be an 8-bit string or a |
| character buffer using the codec for \var{encoding}. The |
| \var{encoding} parameter is a string giving the name of an encoding; |
| if the encoding is not known, \exception{LookupError} is raised. |
| Error handling is done according to \var{errors}; this specifies the |
| treatment of characters which are invalid in the input encoding. If |
| \var{errors} is \code{'strict'} (the default), a |
| \exception{ValueError} is raised on errors, while a value of |
| \code{'ignore'} causes errors to be silently ignored, and a value of |
| \code{'replace'} causes the official Unicode replacement character, |
| \code{U+FFFD}, to be used to replace input characters which cannot |
| be decoded. See also the \refmodule{codecs} module. |
| |
| If no optional parameters are given, \code{unicode()} will mimic the |
| behaviour of \code{str()} except that it returns Unicode strings |
| instead of 8-bit strings. More precisely, if \var{object} is a |
| Unicode string or subclass it will return that Unicode string without |
| any additional decoding applied. |
| |
| For objects which provide a \method{__unicode__()} method, it will |
| call this method without arguments to create a Unicode string. For |
| all other objects, the 8-bit string version or representation is |
| requested and then converted to a Unicode string using the codec for |
| the default encoding in \code{'strict'} mode. |
| |
| \versionadded{2.0} |
| \versionchanged[Support for \method{__unicode__()} added]{2.2} |
| \end{funcdesc} |
| |
| \begin{funcdesc}{vars}{\optional{object}} |
| Without arguments, return a dictionary corresponding to the current |
| local symbol table. With a module, class or class instance object |
| as argument (or anything else that has a \member{__dict__} |
| attribute), returns a dictionary corresponding to the object's |
| symbol table. The returned dictionary should not be modified: the |
| effects on the corresponding symbol table are undefined.\footnote{ |
| In the current implementation, local variable bindings cannot |
| normally be affected this way, but variables retrieved from |
| other scopes (such as modules) can be. This may change.} |
| \end{funcdesc} |
| |
| \begin{funcdesc}{xrange}{\optional{start,} stop\optional{, step}} |
| This function is very similar to \function{range()}, but returns an |
| ``xrange object'' instead of a list. This is an opaque sequence |
| type which yields the same values as the corresponding list, without |
| actually storing them all simultaneously. The advantage of |
| \function{xrange()} over \function{range()} is minimal (since |
| \function{xrange()} still has to create the values when asked for |
| them) except when a very large range is used on a memory-starved |
| machine or when all of the range's elements are never used (such as |
| when the loop is usually terminated with \keyword{break}). |
| |
| \note{\function{xrange()} is intended to be simple and fast. |
| Implementations may impose restrictions to achieve this. |
| The C implementation of Python restricts all arguments to |
| native C longs ("short" Python integers), and also requires |
| that the number of elements fit in a native C long.} |
| \end{funcdesc} |
| |
| \begin{funcdesc}{zip}{\optional{iterable, \moreargs}} |
| This function returns a list of tuples, where the \var{i}-th tuple contains |
| the \var{i}-th element from each of the argument sequences or iterables. |
| The returned list is truncated in length to the length of |
| the shortest argument sequence. When there are multiple arguments |
| which are all of the same length, \function{zip()} is |
| similar to \function{map()} with an initial argument of \code{None}. |
| With a single sequence argument, it returns a list of 1-tuples. |
| With no arguments, it returns an empty list. |
| \versionadded{2.0} |
| |
| \versionchanged[Formerly, \function{zip()} required at least one argument |
| and \code{zip()} raised a \exception{TypeError} instead of returning |
| an empty list]{2.4} |
| \end{funcdesc} |
| |
| |
| % --------------------------------------------------------------------------- |
| |
| |
| \section{Non-essential Built-in Functions \label{non-essential-built-in-funcs}} |
| |
| There are several built-in functions that are no longer essential to learn, |
| know or use in modern Python programming. They have been kept here to |
| maintain backwards compatibility with programs written for older versions |
| of Python. |
| |
| Python programmers, trainers, students and bookwriters should feel free to |
| bypass these functions without concerns about missing something important. |
| |
| |
| \setindexsubitem{(non-essential built-in functions)} |
| |
| \begin{funcdesc}{buffer}{object\optional{, offset\optional{, size}}} |
| The \var{object} argument must be an object that supports the buffer |
| call interface (such as strings, arrays, and buffers). A new buffer |
| object will be created which references the \var{object} argument. |
| The buffer object will be a slice from the beginning of \var{object} |
| (or from the specified \var{offset}). The slice will extend to the |
| end of \var{object} (or will have a length given by the \var{size} |
| argument). |
| \end{funcdesc} |
| |