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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def levenshtein_distance(str_a, str_b):
 """Calculate the Levenshtein distance between string a and b. :param str_a: String - input string a :param str_b: String - input string b :return: Number - Levenshtein Distance between string a and b """

    len_a, len_b = len(str_a), len(str_b)
    if len_a > len_b:
        str_a, str_b = str_b, str_a
        len_a, len_b = len_b, len_a
    current = range(len_a + 1)
    for i in range(1, len_b + 1):
        previous, current = current, [i] + [0] * len_a
        for j in range(1, len_a + 1):
            add, delete = previous[j] + 1, current[j - 1] + 1
            change = previous[j - 1]
            if str_a[j - 1] != str_b[i - 1]:
                change += + 1
            current[j] = min(add, delete, change)
    return current[len_a]