list of tuples to Counter or a dictionary of counts

Question

I have a list of tuples. For each key I'd like to count the number of distinct values.

For example,

Given the following list:

[(k1, 400), (k1, 500), (k2, 600), (k2, 600), (k3, 600)]

I'd like to produce the following:

{k1: 2, k2: 1, k3: 1}

explanation:

k1 has two values (400, 500). k2 has only one value (600)

What's the Pythonic way to do that?

What you have tried and where do you get stuck? Even not very Pythonic. — Daniel Hao, Nov 23 '21 at 12:23
Does this answer your question? [Counting the amount of occurrences in a list of tuples](https://stackoverflow.com/questions/16013485/counting-the-amount-of-occurrences-in-a-list-of-tuples) — Luuk, Nov 23 '21 at 12:31

score 1 · Accepted Answer · answered Nov 23 '21 at 12:26

1

from collections import defaultdict

list_of_tuples = [
    ("k1", 400),
    ("k1", 500),
    ("k2", 600),
    ("k2", 600),
    ("k3", 600),
]

dict_of_sets = defaultdict(set)

for key, value in list_of_tuples:
    dict_of_sets[key].add(value)

result = {key: len(value) for key, value in dict_of_sets.items()}

answered Nov 23 '21 at 12:26

Kyrylo Niedieliev

46
4

Not sure this is considered more `Pythonic`. Find out the link provided by @Luuk by `Counter` is more Pythonic. – Daniel Hao Nov 23 '21 at 13:12

score 0 · Answer 2 · answered Nov 23 '21 at 12:30

0

You can achieve this using Dict Comprehensions, will look something like this:

x = [(k1, 400), (k1, 500), (k2, 600), (k2, 600), (k3, 600)]
dictionary = {k: v for k,v in x}
print(dictionary)

Output:

{'k1': 500, 'k2': 600, 'k3': 600}

answered Nov 23 '21 at 12:30

Victor Corte

46
3

list of tuples to Counter or a dictionary of counts

2 Answers2