operator
— 作为函数的标准运算符
¶
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:
运算符。
lt
(
a
,
b
)
¶
运算符。
le
(
a
,
b
)
¶
运算符。
eq
(
a
,
b
)
¶
运算符。
ne
(
a
,
b
)
¶
运算符。
ge
(
a
,
b
)
¶
运算符。
gt
(
a
,
b
)
¶
运算符。
__lt__
(
a
,
b
)
¶
运算符。
__le__
(
a
,
b
)
¶
运算符。
__eq__
(
a
,
b
)
¶
运算符。
__ne__
(
a
,
b
)
¶
运算符。
__ge__
(
a
,
b
)
¶
运算符。
__gt__
(
a
,
b
)
¶
Perform “rich comparisons” between
a
and
b
. Specifically,
lt(a, b)
相当于
a < b
,
le(a, b)
相当于
a <= b
,
eq(a,
b)
相当于
a == b
,
ne(a, b)
相当于
a != b
,
gt(a, b)
相当于
a > b
and
ge(a, b)
相当于
a
>=
b
. Note that unlike the built-in
cmp()
, these functions can return any value, which may or may not be interpretable as a Boolean value. See
比较
for more information about rich comparisons.
2.2 版新增。
The logical operations are also generally applicable to all objects, and support truth tests, identity tests, and boolean operations:
运算符。
not_
(
obj
)
¶
运算符。
__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.)
运算符。
is_
(
a
,
b
)
¶
返回
a is b
。测试对象身份。
2.3 版新增。
运算符。
is_not
(
a
,
b
)
¶
返回
a is not b
。测试对象身份。
2.3 版新增。
The mathematical and bitwise operations are the most numerous:
运算符。
div
(
a
,
b
)
¶
运算符。
__div__
(
a
,
b
)
¶
返回
a / b
当
__future__.division
is not in effect. This is also known as “classic” division.
运算符。
index
(
a
)
¶
运算符。
__index__
(
a
)
¶
返回
a
converted to an integer. Equivalent to
a.__index__()
.
2.5 版新增。
运算符。
inv
(
obj
)
¶
运算符。
invert
(
obj
)
¶
运算符。
__inv__
(
obj
)
¶
运算符。
__invert__
(
obj
)
¶
Return the bitwise inverse of the number
obj
。这相当于
~obj
.
New in version 2.0:
名称
invert()
and
__invert__()
.
运算符。
truediv
(
a
,
b
)
¶
运算符。
__truediv__
(
a
,
b
)
¶
返回
a / b
当
__future__.division
is in effect. This is also known as “true” division.
2.2 版新增。
Operations which work with sequences (some of them with mappings too) include:
运算符。
包含
(
a
,
b
)
¶
运算符。
__contains__
(
a
,
b
)
¶
Return the outcome of the test
b in a
. Note the reversed operands.
New in version 2.0:
名称
__contains__()
.
运算符。
countOf
(
a
,
b
)
¶
Return the number of occurrences of b in a .
运算符。
delslice
(
a
,
b
,
c
)
¶
运算符。
__delslice__
(
a
,
b
,
c
)
¶
Delete the slice of a from index b to index c-1 .
Deprecated since version 2.6:
This function is removed in Python 3.x. Use
delitem()
with a slice index.
运算符。
getslice
(
a
,
b
,
c
)
¶
运算符。
__getslice__
(
a
,
b
,
c
)
¶
Return the slice of a from index b to index c-1 .
Deprecated since version 2.6:
This function is removed in Python 3.x. Use
getitem()
with a slice index.
运算符。
indexOf
(
a
,
b
)
¶
Return the index of the first of occurrence of b in a .
运算符。
repeat
(
a
,
b
)
¶
运算符。
__repeat__
(
a
,
b
)
¶
Deprecated since version 2.7:
使用
__mul__()
代替。
返回
a * b
where
a
is a sequence and
b
是整数。
运算符。
sequenceIncludes
(
...
)
¶
Deprecated since version 2.0:
使用
contains()
代替。
别名化的
contains()
.
运算符。
setslice
(
a
,
b
,
c
,
v
)
¶
运算符。
__setslice__
(
a
,
b
,
c
,
v
)
¶
Set the slice of a from index b to index c-1 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 “in-place” version. The following functions provide a more primitive access to in-place operators than the usual syntax does; for example, the
语句
x += y
相当于
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
.
运算符。
iconcat
(
a
,
b
)
¶
运算符。
__iconcat__
(
a
,
b
)
¶
a = iconcat(a, b)
相当于
a += b
for
a
and
b
sequences.
2.5 版新增。
运算符。
idiv
(
a
,
b
)
¶
运算符。
__idiv__
(
a
,
b
)
¶
a = idiv(a, b)
相当于
a /= b
当
__future__.division
is not in effect.
2.5 版新增。
运算符。
ifloordiv
(
a
,
b
)
¶
运算符。
__ifloordiv__
(
a
,
b
)
¶
a = ifloordiv(a, b)
相当于
a //= b
.
2.5 版新增。
运算符。
irepeat
(
a
,
b
)
¶
运算符。
__irepeat__
(
a
,
b
)
¶
Deprecated since version 2.7:
使用
__imul__()
代替。
a = irepeat(a, b)
相当于
a *= b
where
a
is a sequence and
b
是整数。
2.5 版新增。
运算符。
itruediv
(
a
,
b
)
¶
运算符。
__itruediv__
(
a
,
b
)
¶
a = itruediv(a, b)
相当于
a /= b
当
__future__.division
is in effect.
2.5 版新增。
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
了解细节)。
运算符。
isCallable
(
obj
)
¶
Deprecated since version 2.0:
使用
isinstance(x, collections.Callable)
代替。
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__()
方法。
运算符。
isMappingType
(
obj
)
¶
Deprecated since version 2.7:
使用
isinstance(x, collections.Mapping)
代替。
Returns true if the object
obj
supports the mapping interface. This is true for dictionaries and all instance objects defining
__getitem__()
.
运算符。
isNumberType
(
obj
)
¶
Deprecated since version 2.7:
使用
isinstance(x, numbers.Number)
代替。
Returns true if the object obj represents a number. This is true for all numeric types implemented in C.
运算符。
isSequenceType
(
obj
)
¶
Deprecated since version 2.7:
使用
isinstance(x, collections.Sequence)
代替。
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.
运算符。
attrgetter
(
attr
)
¶
运算符。
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:
后于
f = attrgetter('name')
, the call
f(b)
返回
b.name
.
后于
f = attrgetter('name', 'date')
, the call
f(b)
返回
(b.name, b.date)
.
后于
f = attrgetter('name.first', 'name.last')
, the call
f(b)
返回
(b.name.first, b.name.last)
.
等效于：
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
2.4 版新增。
Changed in version 2.5: Added support for multiple attributes.
2.6 版改变： Added support for dotted attributes.
运算符。
itemgetter
(
item
)
¶
运算符。
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:
后于
f = itemgetter(2)
, the call
f(r)
返回
r[2]
.
后于
g = itemgetter(2, 5, 3)
, the call
g(r)
返回
(r[2], r[5], r[3])
.
等效于：
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'
2.4 版新增。
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)]
运算符。
methodcaller
(
名称
[
,
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:
后于
f = methodcaller('name')
, the call
f(b)
返回
b.name()
.
后于
f = methodcaller('name', 'foo', bar=1)
, the call
f(b)
返回
b.name('foo', bar=1)
.
等效于：
def methodcaller(name, *args, **kwargs): def caller(obj): return getattr(obj, name)(*args, **kwargs) return caller
2.6 版新增。
This table shows how abstract operations correspond to operator symbols in the Python syntax and the functions in the
operator
模块。
|
操作 |
句法 |
函数 |
|---|---|---|
| Addition |
|
|
| Concatenation |
|
|
| Containment Test |
|
|
| Division |
|
|
| Division |
|
|
| Division |
|
|
| Bitwise And |
|
|
| Bitwise Exclusive Or |
|
|
| Bitwise Inversion |
|
|
| Bitwise Or |
|
|
| 取幂 |
|
|
| Identity |
|
|
| Identity |
|
|
| Indexed Assignment |
|
|
| Indexed Deletion |
|
|
| 索引 |
|
|
| Left Shift |
|
|
| Modulo |
|
|
| Multiplication |
|
|
| Negation (Arithmetic) |
|
|
| Negation (Logical) |
|
|
| Positive |
|
|
| Right Shift |
|
|
| Sequence Repetition |
|
|
| Slice Assignment |
|
|
| Slice Deletion |
|
|
| Slicing |
|
|
| String Formatting |
|
|
| Subtraction |
|
|
| Truth Test |
|
|
| Ordering |
|
|
| Ordering |
|
|
| Equality |
|
|
| Difference |
|
|
| Ordering |
|
|
| Ordering |
|
|