I sometimes need to flatten a list in a list comprehension or generator expression (usually because I'm doing work inside of a template where keeping temporary variables is somewhat painful). This has stumped me for a while but today I found itertools.chain() which worked wonderfully. Here's how I found out I could make use of it:

>>> import itertools
>>> data = [(1,2), (3,4,5), (6,7)]
>>> [i for i in itertools.chain(*data)]
[1, 2, 3, 4, 5, 6, 7]