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Counter and elements() solution in Clear category for Sort Array by Element Frequency by casilda
def frequency_sort(items):
from collections import Counter
# create a dictionary where {k:v} = {k:items.count(k) for k in items}
frequencies = Counter(items)
# sort resulting dictionary by values, in reverse order
# using 'elements' to return each item as many times as its count
ordered = sorted(frequencies.elements(), key=frequencies.get, reverse=True)
return ordered
if __name__ == '__main__':
print("Example:")
print(frequency_sort([4, 6, 2, 2, 6, 4, 4, 4]))
# These "asserts" are used for self-checking and not for an auto-testing
assert list(frequency_sort([4, 6, 2, 2, 6, 4, 4, 4])) == [4, 4, 4, 4, 6, 6, 2, 2]
assert list(frequency_sort(['bob', 'bob', 'carl', 'alex', 'bob'])) == ['bob', 'bob', 'bob', 'carl', 'alex']
assert list(frequency_sort([17, 99, 42])) == [17, 99, 42]
assert list(frequency_sort([])) == []
assert list(frequency_sort([1])) == [1]
print("Coding complete? Click 'Check' to earn cool rewards!")
Sept. 21, 2019
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