a = {
1: {
"a": "aaa",
"b": "bbb",
"c": "ccc"
},
2: {
"d": "ddd",
"a": "abc",
"c": "cca"
},
3: {
"e": "eee",
"a": "ababa",
"b": "bebebe"
}
}
from collections import defaultdict
b = defaultdict(list)
for i, v in a.items():
for j in v:
b[j].append(i)
Результат b
:
defaultdict(<class 'list'>, {'a': [1, 2, 3], 'b': [1, 3], 'c': [1, 2], 'd': [2], 'e': [3]})