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:
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:
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.)
返回 a is b 。测试对象身份。
2.3 版新增。
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:
返回 a / b 当 __future__.division is not in effect. This is also known as “classic” division.
返回 a converted to an integer. Equivalent to a.__index__() .
2.5 版新增。
Return the bitwise inverse of the number obj 。这相当于 ~obj .
New in version 2.0: 名称 invert() and __invert__() .
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:
Return the outcome of the test b in a . Note the reversed operands.
New in version 2.0: 名称 __contains__() .
Return the number of occurrences of b in a .
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.
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.
Return the index of the first of occurrence of b in a .
Deprecated since version 2.7: 使用 __mul__() 代替。
返回 a * b where a is a sequence and b 是整数。
Deprecated since version 2.0: 使用 contains() 代替。
别名化的 contains() .
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 .
a = iconcat(a, b) 相当于 a += b for a and b sequences.
2.5 版新增。
a = idiv(a, b) 相当于 a /= b 当 __future__.division is not in effect.
2.5 版新增。
a = ifloordiv(a, b) 相当于 a //= b .
2.5 版新增。
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。
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)。
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。
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__() .
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.
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.
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:
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.
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:
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)]
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:
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 | 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) |
| 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) |
| 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) |
