按值升序对字典排序，按键按降序对字典排序 [英] Sort a dictionary by values in ascending order and by keys in descending order

问题描述

我正在尝试对字典进行排序，我要遵循的顺序是，首先，字典应该按值以升序进行排序，如果两个或多个键的值相等，那么我想对字典进行排序通过键按降序排列.

I am trying to sort a dictionary, the order which I want to follow is that first, the dictionary should be sorted in increasing order by values and if the values for two or more keys are equal then I want to sort the dictionary by the keys in descending order.

这是代码:

dictionary = {0: 150, 1: 151, 2: 150, 3: 101, 4: 107}
print(sorted(dictionary.items(), key=lambda x: (x[1], x[0])))

我希望输出如下: [(3，101)，(4，107)，(2，150)，(0，150)，(1，151)]

但是输出是: [(3，101)，(4，107)，(0，150)，(2，150)，(1，151)]

推荐答案

由于此处的值是数字，因此可以使用否定键，其作用与反转排序顺序的作用相同:

Because the values are numeric here, you can use negation as having the same effect as reversing the sort order:

sorted(dictionary.items(), key=lambda x: (x[1], -x[0]))

对于更通用的情况，您不能依赖于数字值，这是一种可能的方法，尽管可能有更好的方法.

For the more generic case where you can't rely on the values being numeric, here is a possible approach, although there may be a better way.

from functools import cmp_to_key

def cmp(a, b):
    # https://stackoverflow.com/a/22490617/13596037
    return (a > b) - (a < b)

def cmp_items(a, b):
    """
    compare by second item forward, or if they are the same then use first item
    in reverse direction (returns -1/0/1)
    """
    return cmp(a[1], b[1]) or cmp(b[0], a[0])

dictionary = {0: 150, 1: 151, 2: 150, 3: 101, 4: 107}

print(sorted(dictionary.items(), key=cmp_to_key(cmp_items)))

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