how to append multiple elements to a new list by filter an old one

Question

I have a list like [ ((xs,xe),idx),...]

I want to collect xs and xe into a set,like this way

s={ xs,xe for ((xs,xe),idx)

I know I can use it two times and add xs,xe respectively.

Is there a better way to do it?

Answer 1

You can use itertools.chain.from_iterable

>>> import itertools
>>> lst = [((1,2), 'a'), ((3,4), 'b')]
>>> s = set(itertools.chain.from_iterable(pair for pair, _ in lst))
>>> s
set([1, 2, 3, 4])