以 Python 中的格式（字符串，值）获取列表中每个元组的平均值

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 occurences of the first element of tuples?

I want something like:

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

Answer 1

from collections import defaultdict

sample = [("A", 1), ("B", 2), ("C", 3), ("A", 9), ("B", 8)]

store_alphabet_count = defaultdict(list)

for alphabet, count in sample:
    store_alphabet_count[alphabet].append(count)

result = [
    (key, sum(value) // len(value)) for key, value in store_alphabet_count.items()
]

print(result)

Output:

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

Answer 2

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)]