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from array import array


def edit_distance(str1, str2):
    unsignedShort = 'h'
    distances = [array(unsignedShort, (0,) * (len(str2) + 1)) for i in range(0, len(str1) + 1)]
    # distances[0][0] = 0 since distance between str1[:0] and str2[:0] is 0
    for i in range(1, len(str1) + 1):
        distances[i][0] = i  # Distance between str1[:i] and str2[:0] is i

    for j in range(1, len(str2) + 1):
        distances[0][j] = j  # Distance between str1[:0] and str2[:j] is j

    for i in range(0, len(str1)):
        for j in range(0, len(str2)):
            diff = 0 if str1[i] == str2[j] else 1
            # Deletion, Insertion, Identical / Replacement
            distances[i + 1][j + 1] = min(distances[i + 1][j] + 1, distances[i][j + 1] + 1, distances[i][j] + diff)
    return distances[len(str1)][len(str2)]