9.9. operator
— Standard operators as functions¶
The operator
module exports a set of efficient functions corresponding to
the intrinsic operators of Python. For example, operator.add(x, y)
is
equivalent to the expression x+y
. The function names are those used for
special class methods; variants without leading and trailing __
are also
provided for convenience.
The functions fall into categories that perform object comparisons, logical operations, mathematical operations, sequence operations, and abstract type tests.
The object comparison functions are useful for all objects, and are named after the rich comparison operators they support:

operator.
lt
(a, b)¶ 
operator.
le
(a, b)¶ 
operator.
eq
(a, b)¶ 
operator.
ne
(a, b)¶ 
operator.
ge
(a, b)¶ 
operator.
gt
(a, b)¶ 
operator.
__lt__
(a, b)¶ 
operator.
__le__
(a, b)¶ 
operator.
__eq__
(a, b)¶ 
operator.
__ne__
(a, b)¶ 
operator.
__ge__
(a, b)¶ 
operator.
__gt__
(a, b)¶ Perform “rich comparisons” between a and b. Specifically,
lt(a, b)
is equivalent toa < b
,le(a, b)
is equivalent toa <= b
,eq(a, b)
is equivalent toa == b
,ne(a, b)
is equivalent toa != b
,gt(a, b)
is equivalent toa > b
andge(a, b)
is equivalent toa >= b
. Note that unlike the builtincmp()
, these functions can return any value, which may or may not be interpretable as a Boolean value. See Comparisons for more information about rich comparisons.New in version 2.2.
The logical operations are also generally applicable to all objects, and support truth tests, identity tests, and boolean operations:

operator.
not_
(obj)¶ 
operator.
__not__
(obj)¶ Return the outcome of
not
obj. (Note that there is no__not__()
method for object instances; only the interpreter core defines this operation. The result is affected by the__nonzero__()
and__len__()
methods.)

operator.
truth
(obj)¶ Return
True
if obj is true, andFalse
otherwise. This is equivalent to using thebool
constructor.

operator.
is_
(a, b)¶ Return
a is b
. Tests object identity.New in version 2.3.

operator.
is_not
(a, b)¶ Return
a is not b
. Tests object identity.New in version 2.3.
The mathematical and bitwise operations are the most numerous:

operator.
div
(a, b)¶ 
operator.
__div__
(a, b)¶ Return
a / b
when__future__.division
is not in effect. This is also known as “classic” division.

operator.
index
(a)¶ 
operator.
__index__
(a)¶ Return a converted to an integer. Equivalent to
a.__index__()
.New in version 2.5.

operator.
inv
(obj)¶ 
operator.
invert
(obj)¶ 
operator.
__inv__
(obj)¶ 
operator.
__invert__
(obj)¶ Return the bitwise inverse of the number obj. This is equivalent to
~obj
.New in version 2.0: The names
invert()
and__invert__()
.

operator.
truediv
(a, b)¶ 
operator.
__truediv__
(a, b)¶ Return
a / b
when__future__.division
is in effect. This is also known as “true” division.New in version 2.2.
Operations which work with sequences (some of them with mappings too) include:

operator.
contains
(a, b)¶ 
operator.
__contains__
(a, b)¶ Return the outcome of the test
b in a
. Note the reversed operands.New in version 2.0: The name
__contains__()
.

operator.
countOf
(a, b)¶ Return the number of occurrences of b in a.

operator.
delslice
(a, b, c)¶ 
operator.
__delslice__
(a, b, c)¶ Delete the slice of a from index b to index c1.
Deprecated since version 2.6: This function is removed in Python 3.x. Use
delitem()
with a slice index.

operator.
getslice
(a, b, c)¶ 
operator.
__getslice__
(a, b, c)¶ Return the slice of a from index b to index c1.
Deprecated since version 2.6: This function is removed in Python 3.x. Use
getitem()
with a slice index.

operator.
indexOf
(a, b)¶ Return the index of the first of occurrence of b in a.

operator.
repeat
(a, b)¶ 
operator.
__repeat__
(a, b)¶ Deprecated since version 2.7: Use
__mul__()
instead.Return
a * b
where a is a sequence and b is an integer.

operator.
sequenceIncludes
(...)¶ Deprecated since version 2.0: Use
contains()
instead.Alias for
contains()
.

operator.
setslice
(a, b, c, v)¶ 
operator.
__setslice__
(a, b, c, v)¶ Set the slice of a from index b to index c1 to the sequence v.
Deprecated since version 2.6: This function is removed in Python 3.x. Use
setitem()
with a slice index.
Example use of operator functions:
>>> # Elementwise multiplication
>>> map(mul, [0, 1, 2, 3], [10, 20, 30, 40])
[0, 20, 60, 120]
>>> # Dot product
>>> sum(map(mul, [0, 1, 2, 3], [10, 20, 30, 40]))
200
Many operations have an “inplace” version. The following functions provide a
more primitive access to inplace operators than the usual syntax does; for
example, the statement x += y
is equivalent to
x = operator.iadd(x, y)
. Another way to put it is to say that
z = operator.iadd(x, y)
is equivalent to the compound statement
z = x; z += y
.

operator.
iadd
(a, b)¶ 
operator.
__iadd__
(a, b)¶ a = iadd(a, b)
is equivalent toa += b
.New in version 2.5.

operator.
iand
(a, b)¶ 
operator.
__iand__
(a, b)¶ a = iand(a, b)
is equivalent toa &= b
.New in version 2.5.

operator.
iconcat
(a, b)¶ 
operator.
__iconcat__
(a, b)¶ a = iconcat(a, b)
is equivalent toa += b
for a and b sequences.New in version 2.5.

operator.
idiv
(a, b)¶ 
operator.
__idiv__
(a, b)¶ a = idiv(a, b)
is equivalent toa /= b
when__future__.division
is not in effect.New in version 2.5.

operator.
ifloordiv
(a, b)¶ 
operator.
__ifloordiv__
(a, b)¶ a = ifloordiv(a, b)
is equivalent toa //= b
.New in version 2.5.

operator.
ilshift
(a, b)¶ 
operator.
__ilshift__
(a, b)¶ a = ilshift(a, b)
is equivalent toa <<= b
.New in version 2.5.

operator.
imod
(a, b)¶ 
operator.
__imod__
(a, b)¶ a = imod(a, b)
is equivalent toa %= b
.New in version 2.5.

operator.
imul
(a, b)¶ 
operator.
__imul__
(a, b)¶ a = imul(a, b)
is equivalent toa *= b
.New in version 2.5.

operator.
ior
(a, b)¶ 
operator.
__ior__
(a, b)¶ a = ior(a, b)
is equivalent toa = b
.New in version 2.5.

operator.
ipow
(a, b)¶ 
operator.
__ipow__
(a, b)¶ a = ipow(a, b)
is equivalent toa **= b
.New in version 2.5.

operator.
irepeat
(a, b)¶ 
operator.
__irepeat__
(a, b)¶ Deprecated since version 2.7: Use
__imul__()
instead.a = irepeat(a, b)
is equivalent toa *= b
where a is a sequence and b is an integer.New in version 2.5.

operator.
irshift
(a, b)¶ 
operator.
__irshift__
(a, b)¶ a = irshift(a, b)
is equivalent toa >>= b
.New in version 2.5.

operator.
isub
(a, b)¶ 
operator.
__isub__
(a, b)¶ a = isub(a, b)
is equivalent toa = b
.New in version 2.5.

operator.
itruediv
(a, b)¶ 
operator.
__itruediv__
(a, b)¶ a = itruediv(a, b)
is equivalent toa /= b
when__future__.division
is in effect.New in version 2.5.

operator.
ixor
(a, b)¶ 
operator.
__ixor__
(a, b)¶ a = ixor(a, b)
is equivalent toa ^= b
.New in version 2.5.
The operator
module also defines a few predicates to test the type of
objects; however, these are not all reliable. It is preferable to test
abstract base classes instead (see collections
and
numbers
for details).

operator.
isCallable
(obj)¶ Deprecated since version 2.0: Use
isinstance(x, collections.Callable)
instead.Returns true if the object obj can be called like a function, otherwise it returns false. True is returned for functions, bound and unbound methods, class objects, and instance objects which support the
__call__()
method.

operator.
isMappingType
(obj)¶ Deprecated since version 2.7: Use
isinstance(x, collections.Mapping)
instead.Returns true if the object obj supports the mapping interface. This is true for dictionaries and all instance objects defining
__getitem__()
.

operator.
isNumberType
(obj)¶ Deprecated since version 2.7: Use
isinstance(x, numbers.Number)
instead.Returns true if the object obj represents a number. This is true for all numeric types implemented in C.

operator.
isSequenceType
(obj)¶ Deprecated since version 2.7: Use
isinstance(x, collections.Sequence)
instead.Returns true if the object obj supports the sequence protocol. This returns true for all objects which define sequence methods in C, and for all instance objects defining
__getitem__()
.
The operator
module also defines tools for generalized attribute and item
lookups. These are useful for making fast field extractors as arguments for
map()
, sorted()
, itertools.groupby()
, or other functions that
expect a function argument.

operator.
attrgetter
(attr)¶ 
operator.
attrgetter
(*attrs) Return a callable object that fetches attr from its operand. If more than one attribute is requested, returns a tuple of attributes. The attribute names can also contain dots. For example:
 After
f = attrgetter('name')
, the callf(b)
returnsb.name
.  After
f = attrgetter('name', 'date')
, the callf(b)
returns(b.name, b.date)
.  After
f = attrgetter('name.first', 'name.last')
, the callf(b)
returns(b.name.first, b.name.last)
.
Equivalent to:
def attrgetter(*items): if len(items) == 1: attr = items[0] def g(obj): return resolve_attr(obj, attr) else: def g(obj): return tuple(resolve_attr(obj, attr) for attr in items) return g def resolve_attr(obj, attr): for name in attr.split("."): obj = getattr(obj, name) return obj
New in version 2.4.
Changed in version 2.5: Added support for multiple attributes.
Changed in version 2.6: Added support for dotted attributes.
 After

operator.
itemgetter
(item)¶ 
operator.
itemgetter
(*items) Return a callable object that fetches item from its operand using the operand’s
__getitem__()
method. If multiple items are specified, returns a tuple of lookup values. For example: After
f = itemgetter(2)
, the callf(r)
returnsr[2]
.  After
g = itemgetter(2, 5, 3)
, the callg(r)
returns(r[2], r[5], r[3])
.
Equivalent to:
def itemgetter(*items): if len(items) == 1: item = items[0] def g(obj): return obj[item] else: def g(obj): return tuple(obj[item] for item in items) return g
The items can be any type accepted by the operand’s
__getitem__()
method. Dictionaries accept any hashable value. Lists, tuples, and strings accept an index or a slice:>>> itemgetter(1)('ABCDEFG') 'B' >>> itemgetter(1,3,5)('ABCDEFG') ('B', 'D', 'F') >>> itemgetter(slice(2,None))('ABCDEFG') 'CDEFG'
New in version 2.4.
Changed in version 2.5: Added support for multiple item extraction.
Example of using
itemgetter()
to retrieve specific fields from a tuple record:>>> 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)]
 After

operator.
methodcaller
(name[, args...])¶ Return a callable object that calls the method name on its operand. If additional arguments and/or keyword arguments are given, they will be given to the method as well. For example:
 After
f = methodcaller('name')
, the callf(b)
returnsb.name()
.  After
f = methodcaller('name', 'foo', bar=1)
, the callf(b)
returnsb.name('foo', bar=1)
.
Equivalent to:
def methodcaller(name, *args, **kwargs): def caller(obj): return getattr(obj, name)(*args, **kwargs) return caller
New in version 2.6.
 After
9.9.1. Mapping Operators to Functions¶
This table shows how abstract operations correspond to operator symbols in the
Python syntax and the functions in the operator
module.
Operation  Syntax  Function 

Addition  a + b 
add(a, b) 
Concatenation  seq1 + seq2 
concat(seq1, seq2) 
Containment Test  obj in seq 
contains(seq, obj) 
Division  a / b 
div(a, b) (without
__future__.division ) 
Division  a / b 
truediv(a, b) (with
__future__.division ) 
Division  a // b 
floordiv(a, b) 
Bitwise And  a & b 
and_(a, b) 
Bitwise Exclusive Or  a ^ b 
xor(a, b) 
Bitwise Inversion  ~ a 
invert(a) 
Bitwise Or  a  b 
or_(a, b) 
Exponentiation  a ** b 
pow(a, b) 
Identity  a is b 
is_(a, b) 
Identity  a is not b 
is_not(a, b) 
Indexed Assignment  obj[k] = v 
setitem(obj, k, v) 
Indexed Deletion  del obj[k] 
delitem(obj, k) 
Indexing  obj[k] 
getitem(obj, k) 
Left Shift  a << b 
lshift(a, b) 
Modulo  a % b 
mod(a, b) 
Multiplication  a * b 
mul(a, b) 
Negation (Arithmetic)   a 
neg(a) 
Negation (Logical)  not a 
not_(a) 
Positive  + a 
pos(a) 
Right Shift  a >> b 
rshift(a, b) 
Sequence Repetition  seq * i 
repeat(seq, i) 
Slice Assignment  seq[i:j] = values 
setitem(seq, slice(i, j), values) 
Slice Deletion  del seq[i:j] 
delitem(seq, slice(i, j)) 
Slicing  seq[i:j] 
getitem(seq, slice(i, j)) 
String Formatting  s % obj 
mod(s, obj) 
Subtraction  a  b 
sub(a, b) 
Truth Test  obj 
truth(obj) 
Ordering  a < b 
lt(a, b) 
Ordering  a <= b 
le(a, b) 
Equality  a == b 
eq(a, b) 
Difference  a != b 
ne(a, b) 
Ordering  a >= b 
ge(a, b) 
Ordering  a > b 
gt(a, b) 