如何获取唯一值的索引列表？

Question

Having a list like this

lst = ['a','b','a','c','a','b','b']

I'd like to get lists of indexes for each unique element to get this:

indexes = {
            'a': [0,2,4],
            'b': [1,5,6],
            'c': [3]
          }

This is my current code, but I'm only getting the first index of each element.

indexes= dict()
for el in lst:
    indexes[el] = [lst.index(el)]

>>> indexes
{'a': [0], 'b': [1], 'c': [3]}

Thanks for any help.

Answer 1

The problem with you code is you're overriding the same key again and again but with a different list , so your final dictionary contains only a single list .

you can avoid this behavior by using defaultdict .

from collections import defaultdict

lst = ["a", "b", "a", "c", "a", "b", "b"]
lst = [c for c in lst if c.strip()]  # this will remove empty strings

indexes = defaultdict(list)

for index, char in enumerate(lst):
    indexes[char].append(index)

indexes = dict(indexes)
print(indexes)

Output:

{'a': [0, 2, 4], 'b': [1, 5, 6], 'c': [3]}