How to extract the n-th elements from a list of tuples

user_361427 0
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I'm trying to obtain the n-th elements from a list of tuples.

I have something like:

elements = [(1,1,1),(2,3,7),(3,5,10)]

I wish to extract only the second elements of each tuple into a list:

seconds = [1, 3, 5]

I know that it could be done with a for loop but I wanted to know if there's another way since I have thousands of tuples.

tuples list python
7 Answers

Using islice and chain.from_iterable:

>>> from itertools import chain, islice
>>> elements = [(1,1,1),(2,3,7),(3,5,10)]
>>> list(chain.from_iterable(islice(item, 1, 2) for item in elements))
[1, 3, 5]

This can be useful when you need more than one element:

>>> elements = [(0, 1, 2, 3, 4, 5), 
                (10, 11, 12, 13, 14, 15), 
                (20, 21, 22, 23, 24, 25)]
>>> list(chain.from_iterable(islice(tuple_, 2, 5) for tuple_ in elements))
[2, 3, 4, 12, 13, 14, 22, 23, 24]
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