Combining Dictionaries Of Lists In Python

Question

I have a very large collection of (p, q) tuples that I would like to convert into a dictionary of lists where the first item in each tuple is a key that indexes a list that

Answer 1

Here is the iterator style of doing it

>>> mylist=[(1, 2), (1, 3), (2, 3)]
>>> from itertools import groupby
>>> from operator import itemgetter
>>> mylist=[(1, 2), (1, 3), (2, 3)]
>>> groupby(mylist,itemgetter(0))

>>> list(_)
[(1, ), (2, )]