从字典中一行打印具有相同值的不同键 [英] Printing different keys that have same value in one row from a dictionary

问题描述

这是示例字典.

example = {'a': 10, 'b': 12, 'c': 10, 'd': 12}

我想像下面那样打印它们.

I want to print them like below.

12 b, d
10 a, c

推荐答案

有两种方法可以解决此问题.

There are two ways you can approach this problem.

有效:collections.defaultdict(list)

用倒置的键和值构造一个新字典.重要的是，您可以有重复的值，因此我们使用列表来保存这些值. Pythonic方法是使用collections.defaultdict.

Construct a new dictionary with keys and values inverted. Importantly, you can have duplicate values, so we use a list to hold these. The Pythonic approach is to use collections.defaultdict.

对于非常大的词典，这可能会有很大的内存开销.

For very large dictionaries, this may have a large memory overhead.

example = {'a': 10, 'b': 12, 'c': 10, 'd': 12}

from collections import defaultdict

d = defaultdict(list)

for k, v in example.items():
    d[v].append(k)

for k, v in d.items():
    print(k, ' '.join(v))

10 a c
12 b d

手册:列表理解循环

这种方法在计算上效率低下，但是需要较少的内存开销:

This way is computationally inefficient, but requires less memory overhead:

for value in set(example.values()):
    print(value, ' '.join([k for k, v in example.items() if v == value]))

10 a c
12 b d

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