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Essentially I'm writing a function that receives a list as input and returns a dictionary that counts how many times the data in the list is repeated.

#Example:
count_occurrences(["a", "b", "c", "a", "a," "b"])

#output: 
{"a" : 3, "b" : 2, "c": 1}

My solution so far has been:

def count_occurrences(a_list):
    count_list = {}
    for i in a_list:
        if i not in count_list:
            count_list[i] = 1
        else: 
            count_list[i] += 1 
    return count_list

But I'm wondering if there's a way to use Dictionary Comprehension to shorten/optimize this script.

Keyur Potdar
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Andrew DeNike
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1 Answers1

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There is a built-in class made specifically for this. It's called a Counter and it already implements a dict to you don't need to convert it. 

from collections import Counter

print(Counter(["a", "b", "c", "a", "a", "b"]))

#Output
Counter({'a': 3, 'b': 2, 'c': 1})
Martin
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