如何为降序值编写Python排序键函数

如何为降序值编写Python排序键函数

缓慢但优雅的方法是创建一个具有相反顺序的值包装器：

from functools import total_ordering@total_orderingclass ReversedOrder:    def __init__(self, value):        self.value = value    def __eq__(self, other):        return other.value == self.value    def __lt__(self, other):        return other.value < self.value

如果没有

functools.total_ordering

，则必须实施所有6个比较，例如：

import operatorclass ReversedOrder:    def __init__(self, value):        self.value = valuefor x in ['__lt__', '__le__', '__eq__', '__ne__', '__ge__', '__gt__']:    op = getattr(operator, x)    setattr(ReversedOrder, x, lambda self, other, op=op: op(other.value, self.value))