python3 cmp实现方式

import operator       #首先要导入运算符模块
operator.gt(1,2)      #意思是greater than（大于）
operator.ge(1,2)      #意思是greater and equal（大于等于）
operator.eq(1,2)      #意思是equal（等于）
operator.le(1,2)      #意思是less and equal（小于等于）
operator.lt(1,2)      #意思是less than（小于）

import sys
PY3 = sys.version_info[0] >= 3
if PY3:
    def cmp(a, b):
        return (a > b) - (a < b)
    # mixin class for Python3 supporting __cmp__
    class PY3__cmp__:   
        def __eq__(self, other):
            return self.__cmp__(other) == 0
        def __ne__(self, other):
            return self.__cmp__(other) != 0
        def __gt__(self, other):
            return self.__cmp__(other) > 0
        def __lt__(self, other):
            return self.__cmp__(other) < 0
        def __ge__(self, other):
            return self.__cmp__(other) >= 0
        def __le__(self, other):
            return self.__cmp__(other) <= 0
else:
    class PY3__cmp__:
        pass
class YourClass(PY3__cmp__):
	'''自定义类，可以用list.sort函数或者sorted函数来实现排序。'''
	def __init__(self, name, age):
        self.name = name
        self.age = age
    def __cmp__(self, other):
        return cmp(self.age, other.age)

import operator
lt(a,b) 相当于 a<b     从第一个数字或字母（ASCII）比大小  
le(a,b)相当于a<=b 
eq(a,b)相当于a==b     字母完全一样，返回True, 
ne(a,b)相当于a!=b 
gt(a,b)相当于a>b 
ge(a,b)相当于 a>=b