How to get index of multiple elements of list in python?

Asked Sep 19 '18 at 20:39

Active Sep 19 '18 at 20:39

Viewed 37 times

Let me have a long list:

l = ['a', 'b', 'c', 'a', 'b', 'a', 'c', ...]

I want to get the indices of all 'a'. Unfortunately, l.index('a') will only output the index of 'a''s first occurrence.

I can get them by doing:

[idx for idx,i in enumerate(l) if i == 'a']

Is that the common way, or there is a built-in function?

I am thinking when to use .index if it only outputs the index of the first occurrence.

asked Sep 19 '18 at 20:39

ipramusinto

3

yep the comprehension is an idomatic way – Chris_Rands Sep 19 '18 at 20:41
1

Your list comprehension is how I would write it, too. – timgeb Sep 19 '18 at 20:41
1

I would have gave you the solution you posted – vash_the_stampede Sep 19 '18 at 20:41
You can pass a parameter to [**`list.index`**](https://docs.python.org/3/tutorial/datastructures.html#more-on-lists), to say where to search from. By default it searches from the beginning. – Peter Wood Sep 19 '18 at 20:51

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