\section{\module{operator} ---         Standard operators as functions.}\declaremodule{builtin}{operator}\sectionauthor{Skip Montanaro}{skip@automatrix.com} \modulesynopsis{All Python's standard operators as built-in functions.}  The \module{operator} module exports a set of functions implemented in Ccorresponding to the intrinsic operators of Python.  For example,\code{operator.add(x, y)} is equivalent to the expression \code{x+y}.  Thefunction names are those used for special class methods; variants withoutleading and trailing \samp{__} are also provided for convenience. The functions fall into categories that perform object comparisons,logical operations, mathematical operations, sequence operations, andabstract type tests. The object comparison functions are useful for all objects, and arenamed after the rich comparison operators they support: \begin{funcdesc}{lt}{a, b}\funcline{le}{a, b}\funcline{eq}{a, b}\funcline{ne}{a, b}\funcline{ge}{a, b}\funcline{gt}{a, b}\funcline{__lt__}{a, b}\funcline{__le__}{a, b}\funcline{__eq__}{a, b}\funcline{__ne__}{a, b}\funcline{__ge__}{a, b}\funcline{__gt__}{a, b}Perform ``rich comparisons'' between \var{a} and \var{b}. Specifically,\code{lt(\var{a}, \var{b})} is equivalent to \code{\var{a} < \var{b}},\code{le(\var{a}, \var{b})} is equivalent to \code{\var{a} <= \var{b}},\code{eq(\var{a}, \var{b})} is equivalent to \code{\var{a} == \var{b}},\code{ne(\var{a}, \var{b})} is equivalent to \code{\var{a} != \var{b}},\code{gt(\var{a}, \var{b})} is equivalent to \code{\var{a} > \var{b}}and\code{ge(\var{a}, \var{b})} is equivalent to \code{\var{a} >= \var{b}}.Note that unlike the built-in \function{cmp()}, these functions canreturn any value, which may or may not be interpretable as a Booleanvalue.  See the \citetitle[../ref/ref.html]{Python Reference Manual}for more information about rich comparisons.\versionadded{2.2}\end{funcdesc}  The logical operations are also generally applicable to all objects,and support truth tests, identity tests, and boolean operations: \begin{funcdesc}{not_}{o}\funcline{__not__}{o}Return the outcome of \keyword{not} \var{o}.  (Note that there is no\method{__not__()} method for object instances; only the interpretercore defines this operation.  The result is affected by the\method{__nonzero__()} and \method{__len__()} methods.)\end{funcdesc} \begin{funcdesc}{truth}{o}Return \constant{True} if \var{o} is true, and \constant{False}otherwise.  This is equivalent to using the \class{bool}constructor.\end{funcdesc} \begin{funcdesc}{is_}{a, b}Return \code{\var{a} is \var{b}}.  Tests object identity.\versionadded{2.3}\end{funcdesc} \begin{funcdesc}{is_not}{a, b}Return \code{\var{a} is not \var{b}}.  Tests object identity.\versionadded{2.3}\end{funcdesc}  The mathematical and bitwise operations are the most numerous: \begin{funcdesc}{abs}{o}\funcline{__abs__}{o}Return the absolute value of \var{o}.\end{funcdesc} \begin{funcdesc}{add}{a, b}\funcline{__add__}{a, b}Return \var{a} \code{+} \var{b}, for \var{a} and \var{b} numbers.\end{funcdesc} \begin{funcdesc}{and_}{a, b}\funcline{__and__}{a, b}Return the bitwise and of \var{a} and \var{b}.\end{funcdesc} \begin{funcdesc}{div}{a, b}\funcline{__div__}{a, b}Return \var{a} \code{/} \var{b} when \code{__future__.division} is notin effect.  This is also known as ``classic'' division.\end{funcdesc} \begin{funcdesc}{floordiv}{a, b}\funcline{__floordiv__}{a, b}Return \var{a} \code{//} \var{b}.\versionadded{2.2}\end{funcdesc} \begin{funcdesc}{inv}{o}\funcline{invert}{o}\funcline{__inv__}{o}\funcline{__invert__}{o}Return the bitwise inverse of the number \var{o}.  This is equivalentto \code{\textasciitilde}\var{o}.  The names \function{invert()} and\function{__invert__()} were added in Python 2.0.\end{funcdesc} \begin{funcdesc}{lshift}{a, b}\funcline{__lshift__}{a, b}Return \var{a} shifted left by \var{b}.\end{funcdesc} \begin{funcdesc}{mod}{a, b}\funcline{__mod__}{a, b}Return \var{a} \code{\%} \var{b}.\end{funcdesc} \begin{funcdesc}{mul}{a, b}\funcline{__mul__}{a, b}Return \var{a} \code{*} \var{b}, for \var{a} and \var{b} numbers.\end{funcdesc} \begin{funcdesc}{neg}{o}\funcline{__neg__}{o}Return \var{o} negated.\end{funcdesc} \begin{funcdesc}{or_}{a, b}\funcline{__or__}{a, b}Return the bitwise or of \var{a} and \var{b}.\end{funcdesc} \begin{funcdesc}{pos}{o}\funcline{__pos__}{o}Return \var{o} positive.\end{funcdesc} \begin{funcdesc}{pow}{a, b}\funcline{__pow__}{a, b}Return \var{a} \code{**} \var{b}, for \var{a} and \var{b} numbers.\versionadded{2.3}\end{funcdesc} \begin{funcdesc}{rshift}{a, b}\funcline{__rshift__}{a, b}Return \var{a} shifted right by \var{b}.\end{funcdesc} \begin{funcdesc}{sub}{a, b}\funcline{__sub__}{a, b}Return \var{a} \code{-} \var{b}.\end{funcdesc} \begin{funcdesc}{truediv}{a, b}\funcline{__truediv__}{a, b}Return \var{a} \code{/} \var{b} when \code{__future__.division} is ineffect.  This is also known as ``true'' division.\versionadded{2.2}\end{funcdesc} \begin{funcdesc}{xor}{a, b}\funcline{__xor__}{a, b}Return the bitwise exclusive or of \var{a} and \var{b}.\end{funcdesc} \begin{funcdesc}{index}{a}\funcline{__index__}{a}Return \var{a} converted to an integer.  Equivalent to \var{a}\code{.__index__()}.\versionadded{2.5}\end{funcdesc} Operations which work with sequences include: \begin{funcdesc}{concat}{a, b}\funcline{__concat__}{a, b}Return \var{a} \code{+} \var{b} for \var{a} and \var{b} sequences.\end{funcdesc} \begin{funcdesc}{contains}{a, b}\funcline{__contains__}{a, b}Return the outcome of the test \var{b} \code{in} \var{a}.Note the reversed operands.  The name \function{__contains__()} wasadded in Python 2.0.\end{funcdesc} \begin{funcdesc}{countOf}{a, b}Return the number of occurrences of \var{b} in \var{a}.\end{funcdesc} \begin{funcdesc}{delitem}{a, b}\funcline{__delitem__}{a, b}Remove the value of \var{a} at index \var{b}.\end{funcdesc} \begin{funcdesc}{delslice}{a, b, c}\funcline{__delslice__}{a, b, c}Delete the slice of \var{a} from index \var{b} to index \var{c}\code{-1}.\end{funcdesc} \begin{funcdesc}{getitem}{a, b}\funcline{__getitem__}{a, b}Return the value of \var{a} at index \var{b}.\end{funcdesc} \begin{funcdesc}{getslice}{a, b, c}\funcline{__getslice__}{a, b, c}Return the slice of \var{a} from index \var{b} to index \var{c}\code{-1}.\end{funcdesc} \begin{funcdesc}{indexOf}{a, b}Return the index of the first of occurrence of \var{b} in \var{a}.\end{funcdesc} \begin{funcdesc}{repeat}{a, b}\funcline{__repeat__}{a, b}Return \var{a} \code{*} \var{b} where \var{a} is a sequence and\var{b} is an integer.\end{funcdesc} \begin{funcdesc}{sequenceIncludes}{\unspecified}\deprecated{2.0}{Use \function{contains()} instead.}Alias for \function{contains()}.\end{funcdesc} \begin{funcdesc}{setitem}{a, b, c}\funcline{__setitem__}{a, b, c}Set the value of \var{a} at index \var{b} to \var{c}.\end{funcdesc} \begin{funcdesc}{setslice}{a, b, c, v}\funcline{__setslice__}{a, b, c, v}Set the slice of \var{a} from index \var{b} to index \var{c}\code{-1} to thesequence \var{v}.\end{funcdesc}  Many operations have an ``in-place'' version.  The following functionsprovide a more primitive access to in-place operators than the usualsyntax does; for example, the statement \code{x += y} is equivalent to\code{x = operator.iadd(x, y)}.  Another way to put it is to say that\code{z = operator.iadd(x, y)} is equivalent to the compound statement\code{z = x; z += y}. \begin{funcdesc}{iadd}{a, b}\funcline{__iadd__}{a, b}\code{a = iadd(a, b)} is equivalent to \code{a += b}.\versionadded{2.5}\end{funcdesc} \begin{funcdesc}{iand}{a, b}\funcline{__iand__}{a, b}\code{a = iand(a, b)} is equivalent to \code{a \&= b}.\versionadded{2.5}\end{funcdesc} \begin{funcdesc}{iconcat}{a, b}\funcline{__iconcat__}{a, b}\code{a = iconcat(a, b)} is equivalent to \code{a += b} for \var{a}and \var{b} sequences.\versionadded{2.5}\end{funcdesc} \begin{funcdesc}{idiv}{a, b}\funcline{__idiv__}{a, b}\code{a = idiv(a, b)} is equivalent to \code{a /= b} when\code{__future__.division} is not in effect.\versionadded{2.5}\end{funcdesc} \begin{funcdesc}{ifloordiv}{a, b}\funcline{__ifloordiv__}{a, b}\code{a = ifloordiv(a, b)} is equivalent to \code{a //= b}.\versionadded{2.5}\end{funcdesc} \begin{funcdesc}{ilshift}{a, b}\funcline{__ilshift__}{a, b}\code{a = ilshift(a, b)} is equivalent to \code{a <}\code{<= b}.\versionadded{2.5}\end{funcdesc} \begin{funcdesc}{imod}{a, b}\funcline{__imod__}{a, b}\code{a = imod(a, b)} is equivalent to \code{a \%= b}.\versionadded{2.5}\end{funcdesc} \begin{funcdesc}{imul}{a, b}\funcline{__imul__}{a, b}\code{a = imul(a, b)} is equivalent to \code{a *= b}.\versionadded{2.5}\end{funcdesc} \begin{funcdesc}{ior}{a, b}\funcline{__ior__}{a, b}\code{a = ior(a, b)} is equivalent to \code{a |= b}.\versionadded{2.5}\end{funcdesc} \begin{funcdesc}{ipow}{a, b}\funcline{__ipow__}{a, b}\code{a = ipow(a, b)} is equivalent to \code{a **= b}.\versionadded{2.5}\end{funcdesc} \begin{funcdesc}{irepeat}{a, b}\funcline{__irepeat__}{a, b}\code{a = irepeat(a, b)} is equivalent to \code{a *= b} where\var{a} is a sequence and \var{b} is an integer.\versionadded{2.5}\end{funcdesc} \begin{funcdesc}{irshift}{a, b}\funcline{__irshift__}{a, b}\code{a = irshift(a, b)} is equivalent to \code{a >>= b}.\versionadded{2.5}\end{funcdesc} \begin{funcdesc}{isub}{a, b}\funcline{__isub__}{a, b}\code{a = isub(a, b)} is equivalent to \code{a -= b}.\versionadded{2.5}\end{funcdesc} \begin{funcdesc}{itruediv}{a, b}\funcline{__itruediv__}{a, b}\code{a = itruediv(a, b)} is equivalent to \code{a /= b} when\code{__future__.division} is in effect.\versionadded{2.5}\end{funcdesc} \begin{funcdesc}{ixor}{a, b}\funcline{__ixor__}{a, b}\code{a = ixor(a, b)} is equivalent to \code{a \textasciicircum= b}.\versionadded{2.5}\end{funcdesc}  The \module{operator} module also defines a few predicates to test thetype of objects.  \note{Be careful not to misinterpret theresults of these functions; only \function{isCallable()} has anymeasure of reliability with instance objects.  For example:} \begin{verbatim}>>> class C:...     pass... >>> import operator>>> o = C()>>> operator.isMappingType(o)True\end{verbatim} \begin{funcdesc}{isCallable}{o}\deprecated{2.0}{Use the \function{callable()} built-in function instead.}Returns true if the object \var{o} can be called like a function,otherwise it returns false.  True is returned for functions, bound andunbound methods, class objects, and instance objects which support the\method{__call__()} method.\end{funcdesc} \begin{funcdesc}{isMappingType}{o}Returns true if the object \var{o} supports the mapping interface.This is true for dictionaries and all instance objects defining\method{__getitem__}.\warning{There is no reliable way to test if an instancesupports the complete mapping protocol since the interface itself isill-defined.  This makes this test less useful than it otherwise mightbe.}\end{funcdesc} \begin{funcdesc}{isNumberType}{o}Returns true if the object \var{o} represents a number.  This is truefor all numeric types implemented in C.\warning{There is no reliable way to test if an instancesupports the complete numeric interface since the interface itself isill-defined.  This makes this test less useful than it otherwise mightbe.}\end{funcdesc} \begin{funcdesc}{isSequenceType}{o}Returns true if the object \var{o} supports the sequence protocol.This returns true for all objects which define sequence methods in C,and for all instance objects defining \method{__getitem__}.\warning{There is no reliableway to test if an instance supports the complete sequence interfacesince the interface itself is ill-defined.  This makes this test lessuseful than it otherwise might be.}\end{funcdesc}  Example: Build a dictionary that maps the ordinals from \code{0} to\code{255} to their character equivalents. \begin{verbatim}>>> import operator>>> d = {}>>> keys = range(256)>>> vals = map(chr, keys)>>> map(operator.setitem, [d]*len(keys), keys, vals)\end{verbatim}  The \module{operator} module also defines tools for generalized attributeand item lookups.  These are useful for making fast field extractorsas arguments for \function{map()}, \function{sorted()},\method{itertools.groupby()}, or other functions that expect afunction argument. \begin{funcdesc}{attrgetter}{attr\optional{, args...}}Return a callable object that fetches \var{attr} from its operand.If more than one attribute is requested, returns a tuple of attributes.After, \samp{f=attrgetter('name')}, the call \samp{f(b)} returns\samp{b.name}.  After, \samp{f=attrgetter('name', 'date')}, the call\samp{f(b)} returns \samp{(b.name, b.date)}. \versionadded{2.4}\versionchanged[Added support for multiple attributes]{2.5}\end{funcdesc}    \begin{funcdesc}{itemgetter}{item\optional{, args...}}Return a callable object that fetches \var{item} from its operand.If more than one item is requested, returns a tuple of items.After, \samp{f=itemgetter(2)}, the call \samp{f(b)} returns\samp{b[2]}.After, \samp{f=itemgetter(2,5,3)}, the call \samp{f(b)} returns\samp{(b[2], b[5], b[3])}.		\versionadded{2.4}\versionchanged[Added support for multiple item extraction]{2.5}		\end{funcdesc} Examples:                \begin{verbatim}>>> from operator import itemgetter>>> inventory = [('apple', 3), ('banana', 2), ('pear', 5), ('orange', 1)]>>> getcount = itemgetter(1)>>> map(getcount, inventory)[3, 2, 5, 1]>>> sorted(inventory, key=getcount)[('orange', 1), ('banana', 2), ('apple', 3), ('pear', 5)]\end{verbatim}                 \subsection{Mapping Operators to Functions \label{operator-map}} This table shows how abstract operations correspond to operatorsymbols in the Python syntax and the functions in the\refmodule{operator} module.  \begin{tableiii}{l|c|l}{textrm}{Operation}{Syntax}{Function}  \lineiii{Addition}{\code{\var{a} + \var{b}}}          {\code{add(\var{a}, \var{b})}}  \lineiii{Concatenation}{\code{\var{seq1} + \var{seq2}}}          {\code{concat(\var{seq1}, \var{seq2})}}  \lineiii{Containment Test}{\code{\var{o} in \var{seq}}}          {\code{contains(\var{seq}, \var{o})}}  \lineiii{Division}{\code{\var{a} / \var{b}}}          {\code{div(\var{a}, \var{b}) \#} without \code{__future__.division}}  \lineiii{Division}{\code{\var{a} / \var{b}}}          {\code{truediv(\var{a}, \var{b}) \#} with \code{__future__.division}}  \lineiii{Division}{\code{\var{a} // \var{b}}}          {\code{floordiv(\var{a}, \var{b})}}  \lineiii{Bitwise And}{\code{\var{a} \&\ \var{b}}}          {\code{and_(\var{a}, \var{b})}}  \lineiii{Bitwise Exclusive Or}{\code{\var{a} \^\ \var{b}}}          {\code{xor(\var{a}, \var{b})}}  \lineiii{Bitwise Inversion}{\code{\~{} \var{a}}}          {\code{invert(\var{a})}}  \lineiii{Bitwise Or}{\code{\var{a} | \var{b}}}          {\code{or_(\var{a}, \var{b})}}  \lineiii{Exponentiation}{\code{\var{a} ** \var{b}}}          {\code{pow(\var{a}, \var{b})}}  \lineiii{Identity}{\code{\var{a} is \var{b}}}          {\code{is_(\var{a}, \var{b})}}  \lineiii{Identity}{\code{\var{a} is not \var{b}}}          {\code{is_not(\var{a}, \var{b})}}  \lineiii{Indexed Assignment}{\code{\var{o}[\var{k}] = \var{v}}}          {\code{setitem(\var{o}, \var{k}, \var{v})}}  \lineiii{Indexed Deletion}{\code{del \var{o}[\var{k}]}}          {\code{delitem(\var{o}, \var{k})}}  \lineiii{Indexing}{\code{\var{o}[\var{k}]}}          {\code{getitem(\var{o}, \var{k})}}  \lineiii{Left Shift}{\code{\var{a} <\code{<} \var{b}}}          {\code{lshift(\var{a}, \var{b})}}  \lineiii{Modulo}{\code{\var{a} \%\ \var{b}}}          {\code{mod(\var{a}, \var{b})}}  \lineiii{Multiplication}{\code{\var{a} * \var{b}}}          {\code{mul(\var{a}, \var{b})}}  \lineiii{Negation (Arithmetic)}{\code{- \var{a}}}          {\code{neg(\var{a})}}  \lineiii{Negation (Logical)}{\code{not \var{a}}}

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