Find distance between strings based on non-equal characters count

letters_distance.py

from collections import Counter


def find_letter_distance(string, other):
    string_counter = Counter(string)
    other_counter = Counter(other)

    unique_symbols = set(string + other)
    distance = 0
    for char in unique_symbols:
        string_occurences = string_counter[char]
        other_occurences = other_counter[char]
        distance += abs(string_occurences-other_occurences)
    return distance


def test_find_letter_distance():
    data_string1 = 'one'
    data_other1 = 'two'
    expected1 = 4

    data_string2 = 'equal'
    data_other2 = 'equal'
    expected2 = 0

    data_string3 = 'the length of this string'
    data_other3 = ''
    expected3 = len(data_string3)

    assert find_letter_distance(data_string1, data_other1) == expected1
    assert find_letter_distance(data_string2, data_other2) == expected2
    assert find_letter_distance(data_string3, data_other3) == expected3


if __name__ == '__main__':
    find_letter_distance('one', 'two')