python - How to find all occurrences of an element in a list

Question

index() will give the first occurrence of an item in a list. Is there a neat trick which returns all indices in a list for an element?

Answer 1

You can use a list comprehension:

indices = [i for i, x in enumerate(my_list) if x == "whatever"]

The iterator enumerate(my_list) yields pairs (index, item) for each item in the list. Using i, x as loop variable target unpacks these pairs into the index i and the list item x. We filter down to all x that match our criterion, and select the indices i of these elements.