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Donate← Python Intermediate
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Lesson 9 — Counter
Count in one line
collections.Counter is a dict that counts things for you. Pass it any sequence — a list, or a string of letters — and it returns each item with how many times it appears. most_common(k) gives the k most frequent items.
from collections import Counter
print(Counter(["a", "b", "a"])) # Counter({'a': 2, 'b': 1})
Why it matters: counting votes, words or errors is a common task, and Counter replaces a whole loop.
Want it another way?
Task
Count the letters in "mississippi" and print the Counter.
Run your code — when the output matches the task, you will see a green check. Then mark the lesson complete.
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