Python之operator模块的使用
operator模块的作用
内置操作符的函数接口
使用迭代器编程时，有时需要为简单的表达式创建小函数。有些情况下，尽管这确认可以被实现为lambda函数，但某些操作根本不需要新函数。operator模块定义了一些函数，可以对应标准对象API中内置的算术，比较和其它操作。
1、逻辑操作示例
from operator import not_, truth, is_, is_not a = -1 b = 5 print('a =', a) print('b =', b) print() print('not_(a) :', not_(a)) # 判断是否为空 print('truth(a) :', truth(a)) # 判断对象为0或False，则返回False print('is_(a, b) :', is_(a, b)) # 判断两个值是否相等，相等则返回True print('is_not(a, b):', is_not(a, b)) # 判断两个值是否相等，相等则False
运行效果
a = a b = a is_(a, b) : True is_not(a, b): False
2、比较操作的示例
from operator import lt, le, eq, ne, ge, gt a = 1 b = 5.0 print('a =', a) print('b =', b) for func in (lt, le, eq, ne, ge, gt): print('{}(a, b): {}'.format(func.__name__, func(a, b)))
运行效果
a = 1 b = 5.0 lt(a, b): True le(a, b): True eq(a, b): False ne(a, b): True ge(a, b): False gt(a, b): False
3、算术运算
from operator import abs, neg, pos, add, floordiv, mod, mul, sub, truediv, and_, or_, invert, lshift, rshift, xor a = -1 b = 5.0 c = 2 d = 6 print('a =', a) print('b =', b) print('c =', c) print('d =', d) print('正负数的运算:') print('abs(a):', abs(a)) # 求绝对值 print('neg(a):', neg(a)) # 取反，整数返负数，负数反整数 print('neg(b):', neg(b)) print('pos(a):', pos(a)) # 整数返整数，负数反负数 print('pos(b):', pos(b)) # # print('算术的运算:') print('add(a, b) :', add(a, b)) # 加法 print('floordiv(a, b):', floordiv(a, b)) # 整数除法 print('floordiv(d, c):', floordiv(d, c)) print('mod(a, b) :', mod(a, b)) # 取模 print('mul(a, b) :', mul(a, b)) # 乘法 print('pow(c, d) :', pow(c, d)) # 开方 print('sub(b, a) :', sub(b, a)) # 减法 print('truediv(a, b) :', truediv(a, b)) # 除法 print('truediv(d, c) :', truediv(d, c)) # # print('\nBitwise:') print('and_(c, d) :', and_(c, d)) # 且运算 print('invert(c) :', invert(c)) # 位取反运算 print('lshift(c, d):', lshift(c, d)) # 左位移 print('or_(c, d) :', or_(c, d)) # 或运算 print('rshift(d, c):', rshift(d, c)) # 右位移 print('xor(c, d) :', xor(c, d)) # 取反运算
运行效果
a = -1 b = 5.0 c = 2 d = 6 正负数的运算: abs(a): 1 neg(a): 1 neg(b): -5.0 pos(a): -1 pos(b): 5.0 add(a, b) : 4.0 floordiv(a, b): -1.0 floordiv(d, c): 3 mod(a, b) : 4.0 mul(a, b) : -5.0 pow(c, d) : 64 sub(b, a) : 6.0 truediv(a, b) : -0.2 truediv(d, c) : 3.0 and_(c, d) : 2
4、列表进阶的操作示例
from operator import * a = [1, 2, 3] b = ['a', 'b', 'c'] print('a =', a) print('b =', b) print('\nConstructive:') print(' concat(a, b):', concat(a, b)) # 列表连接 print('\nSearching:') print(' contains(a, 1) :', contains(a, 1)) # 判断a列表是否包含1 print(' contains(b, "d"):', contains(b, "d")) # 判断b列表是否包含d print(' countOf(a, 1) :', countOf(a, 1)) # 获取a列表，1元素的个数 print(' countOf(b, "d") :', countOf(b, "d")) # 获取b列表，d元素的个数 print(' indexOf(a, 5) :', indexOf(a, 1)) # 在a列表中，1元素的下标位置 print('\nAccess Items:') print(' getitem(b, 1) :', getitem(b, 1)) # 获取b列表下标为1的元素 print(' getitem(b, slice(1, 3)) :', getitem(b, slice(1, 3))) # 切片取元素 print(' setitem(b, 1, "d") :', end=' ') setitem(b, 1, "d") # 在下标1设置元素d print(b) print(' setitem(a, slice(1, 3), [4, 5]):', end=' ') setitem(a, slice(1, 3), [4, 5]) # 切片获取元素，并且修改元素 print(a) print('\nDestructive:') print(' delitem(b, 1) :', end=' ') delitem(b, 1) # 删除下标为1的元素 print(b) print(' delitem(a, slice(1, 3)):', end=' ') delitem(a, slice(1, 3)) # 切片获取元素，并且删除 print(a)
运行效果
a = [1, 2, 3] b = ['a', 'b', 'c'] Constructive: concat(a, b): [1, 2, 3, 'a', 'b', 'c'] Searching: contains(a, 1) : True contains(b, "d"): False countOf(a, 1) : 1 countOf(b, "d") : 0 indexOf(a, 5) : 0 Access Items: getitem(b, 1) : b getitem(b, slice(1, 3)) : ['b', 'c'] setitem(b, 1, "d") : ['a', 'd', 'c'] setitem(a, slice(1, 3), [4, 5]): [1, 4, 5] Destructive: delitem(b, 1) : ['a', 'c'] delitem(a, slice(1, 3)): [1]
5、在原来的元素进行运算的示例
from operator import iadd, iconcat a = -1 b = 5.0 c = [1, 2, 3] d = ['a', 'b', 'c'] print('a =', a) print('b =', b) print('c =', c) print('d =', d) print() a = iadd(a, b) # a += b ,相当于在原来的元素进行相加 print('a = iadd(a, b) =>', a) print() c = iconcat(c, d) # a += b, print('c = iconcat(c, d) =>', c)
运行效果
a = -1 b = 5.0 c = [1, 2, 3] d = ['a', 'b', 'c'] a = iadd(a, b) => 4.0 c = iconcat(c, d) => [1, 2, 3, 'a', 'b', 'c']
6、类属性和元素的获取方法
from operator import * class MyObj: """example class for attrgetter""" def __init__(self, arg): super().__init__() self.arg = arg def __repr__(self): return 'MyObj({})'.format(self.arg) l = [MyObj(i) for i in range(5)] print('objects :', l) # Extract the 'arg' value from each object g = attrgetter('arg') vals = [g(i) for i in l] print('arg values:', vals) # Sort using arg l.reverse() print('reversed :', l) print('sorted :', sorted(l, key=g))
运行效果
objects : [MyObj(0), MyObj(1), MyObj(2), MyObj(3), MyObj(4)] arg values: [0, 1, 2, 3, 4] reversed : [MyObj(4), MyObj(3), MyObj(2), MyObj(1), MyObj(0)] sorted : [MyObj(0), MyObj(1), MyObj(2), MyObj(3), MyObj(4)]
7、获取字典或元组的值或key,然后进行排序的示例（推荐）
from operator import itemgetter l = [dict(val=-1 * i) for i in range(4)] print('Dictionaries:') print(' original:', l) g = itemgetter('val') vals = [g(i) for i in l] print(' values:', vals) print(' sorted:', sorted(l, key=g)) print() l = [(i, i * -2) for i in range(4)] print('\nTuples:') print(' original:', l) g = itemgetter(1) vals = [g(i) for i in l] print(' values:', vals) print(' sorted:', sorted(l, key=g))
运行效果
Dictionaries: original: [{'val': 0}, {'val': -1}, {'val': -2}, {'val': -3}] values: [0, -1, -2, -3] sorted: [{'val': -3}, {'val': -2}, {'val': -1}, {'val': 0}] Tuples: original: [(0, 0), (1, -2), (2, -4), (3, -6)] values: [0, -2, -4, -6] sorted: [(3, -6), (2, -4), (1, -2), (0, 0)]
8、进行类的比较和算术运算
from operator import * class MyObj: """Example for operator overloading""" def __init__(self, val): super(MyObj, self).__init__() self.val = val def __str__(self): return 'MyObj({})'.format(self.val) def __lt__(self, other): """compare for less-than""" print('Testing {} < {}'.format(self, other)) return self.val < other.val def __add__(self, other): """add values""" print('Adding {} + {}'.format(self, other)) return MyObj(self.val + other.val) a = MyObj(1) b = MyObj(2) print('Comparison:') print(lt(a, b)) print('\nArithmetic:') print(add(a, b))
运行效果
Comparison: Testing MyObj(1) < MyObj(2) True Arithmetic: Adding MyObj(1) + MyObj(2) MyObj(3)
