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operator — 作为函数的标准运算符
- 将运算符映射到函数
- 原位运算符

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`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 . Many function names are those used for special methods, without the double underscores. For backward compatibility, many of these have a variant with the double underscores kept. The variants without the double underscores are preferred for clarity.

The functions fall into categories that perform object comparisons, logical operations, mathematical operations and sequence operations.

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 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.

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 __bool__() and __len__() methods.)

运算符。 truth ( obj ) ¶: 返回 True if obj 为 True，和 False 否则。这相当于使用 bool 构造函数。

运算符。 is_ ( a , b ) ¶: 返回 a is b 。测试对象身份。

运算符。 is_not ( a , b ) ¶: 返回 a is not b 。测试对象身份。

The mathematical and bitwise operations are the most numerous:

运算符。 abs ( obj ) ¶
运算符。 __abs__ ( obj ) ¶: 返回绝对值的 obj .

运算符。 add ( a , b ) ¶
运算符。 __add__ ( a , b ) ¶: 返回 a + b , for a and b numbers.

运算符。 and_ ( a , b ) ¶
运算符。 __and__ ( a , b ) ¶: Return the bitwise and of a and b .

运算符。 floordiv ( a , b ) ¶
运算符。 __floordiv__ ( a , b ) ¶: 返回 a // b .

运算符。 index ( a ) ¶

运算符。 __index__ ( a ) ¶

返回 a converted to an integer. Equivalent to a.__index__() .

3.10 版改变： The result always has exact type int . Previously, the result could have been an instance of a subclass of int .

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 .

运算符。 lshift ( a , b ) ¶
运算符。 __lshift__ ( a , b ) ¶: 返回 a shifted left by b .

运算符。 mod ( a , b ) ¶
运算符。 __mod__ ( a , b ) ¶: 返回 a % b .

运算符。 mul ( a , b ) ¶
运算符。 __mul__ ( a , b ) ¶: 返回 a * b , for a and b numbers.

运算符。 matmul ( a , b ) ¶

运算符。 __matmul__ ( a , b ) ¶

返回 a @ b .

Added in version 3.5.

运算符。 neg ( obj ) ¶
运算符。 __neg__ ( obj ) ¶: 返回 obj negated ( -obj ).

运算符。 or_ ( a , b ) ¶
运算符。 __or__ ( a , b ) ¶: Return the bitwise or of a and b .

运算符。 pos ( obj ) ¶
运算符。 __pos__ ( obj ) ¶: 返回 obj positive ( +obj ).

运算符。 pow ( a , b ) ¶
运算符。 __pow__ ( a , b ) ¶: 返回 a ** b , for a and b numbers.

运算符。 rshift ( a , b ) ¶
运算符。 __rshift__ ( a , b ) ¶: 返回 a shifted right by b .

运算符。 sub ( a , b ) ¶
运算符。 __sub__ ( a , b ) ¶: 返回 a - b .

运算符。 truediv ( a , b ) ¶
运算符。 __truediv__ ( a , b ) ¶: 返回 a / b where 2/3 is .66 rather than 0. This is also known as “true” division.

运算符。 xor ( a , b ) ¶
运算符。 __xor__ ( a , b ) ¶: Return the bitwise exclusive or of a and b .

Operations which work with sequences (some of them with mappings too) include:

运算符。 concat ( a , b ) ¶
运算符。 __concat__ ( a , b ) ¶: 返回 a + b for a and b sequences.

运算符。 contains ( a , b ) ¶
运算符。 __contains__ ( a , b ) ¶: Return the outcome of the test b in a . Note the reversed operands.

运算符。 countOf ( a , b ) ¶: Return the number of occurrences of b in a .

运算符。 delitem ( a , b ) ¶
运算符。 __delitem__ ( a , b ) ¶: Remove the value of a at index b .

运算符。 getitem ( a , b ) ¶
运算符。 __getitem__ ( a , b ) ¶: Return the value of a at index b .

运算符。 indexOf ( a , b ) ¶: Return the index of the first of occurrence of b in a .

运算符。 setitem ( a , b , c ) ¶
运算符。 __setitem__ ( a , b , c ) ¶: Set the value of a at index b to c .

运算符。 length_hint ( obj , default = 0 ) ¶

Return an estimated length for the object obj . First try to return its actual length, then an estimate using object.__length_hint__() , and finally return the default value.

Added in version 3.4.

The following operation works with callables:

运算符。 call ( obj , / , * args , ** kwargs ) ¶

运算符。 __call__ ( obj , / , * args , ** kwargs ) ¶

返回 obj(*args, **kwargs) .

Added in version 3.11.

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 any(not isinstance(item, str) for item in items):
        raise TypeError('attribute name must be a string')
    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

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'
>>> soldier = dict(rank='captain', name='dotterbart')
>>> itemgetter('rank')(soldier)
'captain'

Example of using itemgetter() to retrieve specific fields from a tuple record:

>>> inventory = [('apple', 3), ('banana', 2), ('pear', 5), ('orange', 1)]
>>> getcount = itemgetter(1)
>>> list(map(getcount, inventory))
[3, 2, 5, 1]
>>> sorted(inventory, key=getcount)
[('orange', 1), ('banana', 2), ('apple', 3), ('pear', 5)]

运算符。 methodcaller ( name , / , * args , ** kwargs ) ¶

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

将运算符映射到函数 ¶

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	`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)`
取幂	`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)`
索引	`obj[k]`	`getitem(obj, k)`
Left Shift	`a << b`	`lshift(a, b)`
Modulo	`a % b`	`mod(a, b)`
Multiplication	`a * b`	`mul(a, b)`
Matrix Multiplication	`a @ b`	`matmul(a, b)`
Negation (Arithmetic)	`- a`	`neg(a)`
Negation (Logical)	`not a`	`not_(a)`
Positive	`+ a`	`pos(a)`
Right Shift	`a >> b`	`rshift(a, b)`
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)`

原位运算符 ¶

Many operations have an “in-place” version. Listed below are functions providing 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 .

In those examples, note that when an in-place method is called, the computation and assignment are performed in two separate steps. The in-place functions listed below only do the first step, calling the in-place method. The second step, assignment, is not handled.

For immutable targets such as strings, numbers, and tuples, the updated value is computed, but not assigned back to the input variable:

>>> a = 'hello'
>>> iadd(a, ' world')
'hello world'
>>> a
'hello'

For mutable targets such as lists and dictionaries, the in-place method will perform the update, so no subsequent assignment is necessary:

>>> s = ['h', 'e', 'l', 'l', 'o']
>>> iadd(s, [' ', 'w', 'o', 'r', 'l', 'd'])
['h', 'e', 'l', 'l', 'o', ' ', 'w', 'o', 'r', 'l', 'd']
>>> s
['h', 'e', 'l', 'l', 'o', ' ', 'w', 'o', 'r', 'l', 'd']

运算符。 iadd ( a , b ) ¶
运算符。 __iadd__ ( a , b ) ¶: a = iadd(a, b) 相当于 a += b .

运算符。 iand ( a , b ) ¶
运算符。 __iand__ ( a , b ) ¶: a = iand(a, b) 相当于 a &= b .

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.

运算符。 ifloordiv ( a , b ) ¶
运算符。 __ifloordiv__ ( a , b ) ¶: a = ifloordiv(a, b) 相当于 a //= b .

运算符。 ilshift ( a , b ) ¶
运算符。 __ilshift__ ( a , b ) ¶: a = ilshift(a, b) 相当于 a <<= b .

运算符。 imod ( a , b ) ¶
运算符。 __imod__ ( a , b ) ¶: a = imod(a, b) 相当于 a %= b .

运算符。 imul ( a , b ) ¶
运算符。 __imul__ ( a , b ) ¶: a = imul(a, b) 相当于 a *= b .

运算符。 imatmul ( a , b ) ¶

运算符。 __imatmul__ ( a , b ) ¶

a = imatmul(a, b) 相当于 a @= b .

Added in version 3.5.

运算符。 ior ( a , b ) ¶
运算符。 __ior__ ( a , b ) ¶: a = ior(a, b) 相当于 a |= b .

运算符。 ipow ( a , b ) ¶
运算符。 __ipow__ ( a , b ) ¶: a = ipow(a, b) 相当于 a **= b .

运算符。 irshift ( a , b ) ¶
运算符。 __irshift__ ( a , b ) ¶: a = irshift(a, b) 相当于 a >>= b .

运算符。 isub ( a , b ) ¶
运算符。 __isub__ ( a , b ) ¶: a = isub(a, b) 相当于 a -= b .

运算符。 itruediv ( a , b ) ¶
运算符。 __itruediv__ ( a , b ) ¶: a = itruediv(a, b) 相当于 a /= b .

运算符。 ixor ( a , b ) ¶
运算符。 __ixor__ ( a , b ) ¶: a = ixor(a, b) 相当于 a ^= b .

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