Flatten a list in python
python
Solution
If you just want to flatten the list, just use `itertools.chain.from_iterable`: http://docs.python.org/library/itertools.html#itertools.chain.from_iterable
Problem
I have a list like this: ``` [[(video1,4)], [(video2,5),(video3,8)], [(video1,5)], [(video5, 7), (video6,9)]...] ``` each item in this list may contain a single data pair, or a tuple, I want to change this list into ``` [(video1,4),(video2,5),(video3,8),(video1,5),(video5,7),(video6,9)...] ``` then do this: ``` for item in list: reqs = reqs + item[1] b.append(item[0]) c = set(b) ``` I don't know how to change the list structure, or how to do the same calculation based on the original list?