Given a list of lists, find the index of the list which contains a particular item in Python

Question

For example, I have a list of lists:

[[1,2],[3,4],[5,6]]

Given element 3, I need the index of the list it belongs to, i.e. 1.

The lists have mutually exclusive elements.

Answer 1

Here's a quick solution, although it does build a temporary list:

>>> x = [[1,2],[3,4],[5,6]]
>>> v = 3
>>> [v in y for y in x].index(True)
1
>>>