CODEWITHSUNDEEP
pythonlistpython-2.7tupleselement
Nick
Nick

Reputation: 27

finding all iterations of an element in a tuple and returning its pair

So I have a list of tuples that looks something like:

visits_country = (['123', 'United States'], ['456', 'United States'], ['1', 'Canada'], ['24', 'Canada'], ['12', 'Mexico'])

I've managed to sum all of the first entries which have a second entry 'United States' as follows

us_visits = [x[0] for x in visits_country if x[1] == 'United States']
total_us_visits = sum(map(int, us_visits))

Is there a way to automate this task so that I don't have to write a whole new line for every single country to sum all of its paired integers? Possibly a function that will return a list with each unique country and its total visits from each occurrence in the original list (visits_country)?

Thanks!

Upvotes: 0

Views: 41

Answers (2)

JRazor
JRazor

Reputation: 2817

Easy:

visits_country = (['123', 'United States'], ['456', 'United States'], 
                  ['1', 'Canada'], ['24', 'Canada'], ['12', 'Mexico'])

dictionary = {}

for count, country in visits_country:
    dictionary[country] = dictionary.get(country, 0) + int(count)

print dictionary

Upvotes: 3

ShadowRanger
ShadowRanger

Reputation: 155506

Yup. The most obvious approaches are to use either collections.Counter or itertools.groupby, the latter requiring a presort. For example:

from itertools import groupby
from operator import itemgetter

visits_country.sort(itemgetter(1))
sums = [(sum(int(x) for _, x in grp), key)
        for key, grp in groupby(visits_country, itemgetter(1))]

or:

from collections import Counter

counts = Counter()
for visits, country in visits_country:
    counts[country] += int(visits)

Upvotes: 0

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