How do I sum the first value in each tuple in a list of tuples in Python?

Question

I have a list of tuples (always pairs) like this:

[(0, 1), (2, 3), (5, 7), (2, 1)]

I\'d like to find the sum of the first items in each pai

Answer 1

If you have a very large list or a generator that produces a large number of pairs you might want to use a generator based approach. For fun I use itemgetter() and imap(), too. A simple generator based approach might be enough, though.

import operator
import itertools

idx0 = operator.itemgetter(0)
list_of_pairs = [(0, 1), (2, 3), (5, 7), (2, 1)]
sum(itertools.imap(idx0, list_of_pairs))

Note that itertools.imap() is available in Python >= 2.3. So you can use a generator based approach there, too.