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author | cinap_lenrek <cinap_lenrek@localhost> | 2011-05-03 11:25:13 +0000 |
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committer | cinap_lenrek <cinap_lenrek@localhost> | 2011-05-03 11:25:13 +0000 |
commit | 458120dd40db6b4df55a4e96b650e16798ef06a0 (patch) | |
tree | 8f82685be24fef97e715c6f5ca4c68d34d5074ee /sys/src/cmd/python/Doc/lib/libfuncs.tex | |
parent | 3a742c699f6806c1145aea5149bf15de15a0afd7 (diff) |
add hg and python
Diffstat (limited to 'sys/src/cmd/python/Doc/lib/libfuncs.tex')
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diff --git a/sys/src/cmd/python/Doc/lib/libfuncs.tex b/sys/src/cmd/python/Doc/lib/libfuncs.tex new file mode 100644 index 000000000..84f56d873 --- /dev/null +++ b/sys/src/cmd/python/Doc/lib/libfuncs.tex @@ -0,0 +1,1321 @@ +\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 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 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 + \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}}} + 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}{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 + (new-style class) and \var{object} is an object of that type or of a + (direct or indirect) subclass thereof. 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}{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, iterable\optional{, initializer}} + Apply \var{function} of two arguments cumulatively to the items of + \var{iterable}, from left to right, so as to reduce the iterable 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{iterable}. If the optional + \var{initializer} is present, it is placed before the items of the + iterable in the calculation, and serves as a default when the + iterable is empty. If \var{initializer} is not given and + \var{iterable} 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} + + 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})}. + Note that \code{sum(range(\var{n}), \var{m})} is equivalent to + \code{reduce(operator.add, range(\var{n}), \var{m})} + \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}{apply}{function, args\optional{, keywords}} + The \var{function} argument must be a callable object (a + user-defined or built-in function or method, or a class object) and + the \var{args} argument must be a sequence. The \var{function} is + called with \var{args} as the argument list; the number of arguments + is the length of the tuple. + If the optional \var{keywords} argument is present, it must be a + dictionary whose keys are strings. It specifies keyword arguments + to be added to the end of the argument list. + Calling \function{apply()} is different from just calling + \code{\var{function}(\var{args})}, since in that case there is always + exactly one argument. The use of \function{apply()} is equivalent + to \code{\var{function}(*\var{args}, **\var{keywords})}. + Use of \function{apply()} is not necessary since the ``extended call + syntax,'' as used in the last example, is completely equivalent. + + \deprecated{2.3}{Use the extended call syntax instead, as described + above.} +\end{funcdesc} + +\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} + +\begin{funcdesc}{coerce}{x, y} + Return a tuple consisting of the two numeric arguments converted to + a common type, using the same rules as used by arithmetic + operations. If coercion is not possible, raise \exception{TypeError}. +\end{funcdesc} + +\begin{funcdesc}{intern}{string} + Enter \var{string} in the table of ``interned'' strings and return + the interned string -- which is \var{string} itself or a copy. + Interning strings is useful to gain a little performance on + dictionary lookup -- if the keys in a dictionary are interned, and + the lookup key is interned, the key comparisons (after hashing) can + be done by a pointer compare instead of a string compare. Normally, + the names used in Python programs are automatically interned, and + the dictionaries used to hold module, class or instance attributes + have interned keys. \versionchanged[Interned strings are not + immortal (like they used to be in Python 2.2 and before); + you must keep a reference to the return value of \function{intern()} + around to benefit from it]{2.3} +\end{funcdesc} |