Add values in a list of tuples if one element is repeated

Question

I have a list of tuples as:

values = [('n', 2), ('b', 5), ('d',6), ('b',3)]

I would like to add the integer value if the first element is the same so I get a new list as:

valuesNew = [('n', 2), ('b', 8), ('d',6)]

I would appreciate any help. Thanks!

Thanks for accepting my answer. I recommend you take a look at some of the answers on the linked page, as they are a lot more clever than mine :) — Tom Fenech, May 22 '14 at 17:18

score 1 · Accepted Answer · answered May 22 '14 at 17:03

Here's one way you could do it. You lose the ordering of the original tuple, as dictionaries aren't ordered.

d = dict()
for key, val in values:
    if key in d:
        d[key] += val
    else:
        d[key] = val

valuesNew = [(k,v) for k,v in d.iteritems()]

gives you:

>>> valuesNew
[('b', 8), ('d', 6), ('n', 2)]

Add values in a list of tuples if one element is repeated

1 Answers1