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

itertools.groupby can do what you want:

import itertools
import operator

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

def accumulate(l):
    it = itertools.groupby(l, operator.itemgetter(0))
    for key, subiter in it:
       yield key, sum(item[1] for item in subiter) 

>>> print list(accumulate(L))
[('grape', 103), ('apple', 29), ('banana', 3)]
>>>