:mod:`operator` --- Standard operators as functions
The :mod:`operator` module exports a set of functions implemented in C
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:
The logical operations are also generally applicable to all objects, and support truth tests, identity tests, and boolean operations:
The mathematical and bitwise operations are the most numerous:
Operations which work with sequences include:
Many operations have an "in-place" version. The following functions provide a
more primitive access to in-place operators than the usual syntax does; for
example, the :term:`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.
Example: Build a dictionary that maps the ordinals from 0 to 255 to
their character equivalents.
>>> d = {}
>>> keys = range(256)
>>> vals = map(chr, keys)
>>> map(operator.setitem, [d]*len(keys), keys, vals) # doctest: +SKIP
The :mod:`operator` module also defines tools for generalized attribute and item lookups. These are useful for making fast field extractors as arguments for :func:`map`, :func:`sorted`, :meth:`itertools.groupby`, or other functions that expect a function argument.
Mapping Operators to Functions
This table shows how abstract operations correspond to operator symbols in the Python syntax and the functions in the :mod:`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 |
truediv(a, b) |
| 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) |
| Right Shift | a >> b |
rshift(a, b) |
| 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) |