How to find the index of an item in a list, but not an exact match

Question

I have a list something like this:

ls = ['item1', 'this is item2', 'item3']

I want to be able to find the index of the item 'this is item2' by searching for 'item2' . The index function is looking for the exact match so it wouldn't help here:

index = ls.index('item2')

How can I achieve this requirement?

Answer 1

Here's a solution using next with a generator, and enumerate to get the index:

>>> ls = ['item1', 'this is item2', 'item3']
>>> next(i for i, v in enumerate(ls) if 'item2' in v)
1

It will raise StopIteration if the item is not found. If you want None or -1 instead, you can give it as the second argument to next :

>>> next((i for i, v in enumerate(ls) if 'item5' in v), -1)
-1

Answer 2

You may simply pass by a temporary list and apply index method on it:

ls = ['item1', 'this is item2', 'item3']
index = ['item2' in item for item in ls].index(True)