Grouping Python tuple list

Question

I have a list of (label, count) tuples like this:

[(\'grape\', 100), (\'grape\', 3), (\'apple\', 15), (\'apple\', 10), (\'apple\', 4), (\'banana\', 3)]
         


        

Answer 1

using itertools and list comprehensions

import itertools

[(key, sum(num for _, num in value))
    for key, value in itertools.groupby(l, lambda x: x[0])]

Edit: as gnibbler pointed out: if l isn't already sorted replace it with sorted(l).