Get mean of values for each tuple in a list in the format (string, value) in Python

Question

I have a list of tuples like

(A, 1), (B, 2), (C, 3), (A, 9), (B, 8).

How to get the mean of each value referred to the first element of the tuples, not knowing the number of occurrences of the first element of tuples?

I want something like:

(A, 5), (B, 5), (C, 3).

Answer 1

Using groupby and itemgetter:

from itertools import groupby

from operator import itemgetter

from statistics import mean

s = [('A', 1), ('B', 2), ('C', 3), ('A', 9), ('B', 8)]

s2 = sorted(s, key=itemgetter(0))   # sorting the tuple based on 0th index

print([(k, int(mean(list(zip(*g))[1]))) for k, g in groupby(s2, itemgetter(0))])

OUTPUT:

[('A', 5), ('B', 5), ('C', 3)]

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