Python - 逆字典值列表

给定字典作为值列表，将其反转，即将列表中的元素映射到键并创建新的值列表。

Input : test_dict = {1: [2, 3], 2: [3], 3: [1]}
Output : {2: [1], 3: [1, 2], 1: [3]}
Explanation : List elements mapped with their keys.

Input : test_dict = {1: [2, 3, 4]}
Output : {2: [1], 3: [1], 4: [1]}
Explanation : List elements mapped with their keys.

方法：使用 defaultdict() + 循环

这是可以执行此任务的一种方式。在此，我们使用字典列表初始化结果键，并使用循环迭代为每个值分配其键，并改造结果字典值列表。

Python3

# Python3 code to demonstrate working of 
# Inverse Dictionary Values List
# Using 
from collections import defaultdict
  
# initializing dictionary
test_dict = {1: [2, 3], 2: [3], 3: [1], 4: [2, 1]}
  
# printing original dictionary
print("The original dictionary is : " + str(test_dict))
  
# initializing empty list as Values
res = defaultdict(list)                                                                 
  
# using loop to perform reverse mapping
for keys, vals in test_dict.items(): 
   for val in vals: 
       res[val].append(keys)
  
# printing result 
print("The required result : " + str(dict(res)))

输出

The original dictionary is : {1: [2, 3], 2: [3], 3: [1], 4: [2, 1]}
The required result : {2: [1, 4], 3: [1, 2], 1: [3, 4]}