Python HW - Merge sort

merge_sort.py

from random import randint

def string_compare(s1, s2):
    rv = len(s1) - len(s2)
    # print(f'values: ({s1}, {s2}); {s1} > {s2} ? {rv}')
    if rv > 0:
        return 1
    elif rv < 0:
        return -1
    else:
        return 0

def int_compare(i1, i2):
    rv = i1 - i2
    # print(f'values: ({i1}, {i2}); {i1} > {i2} ? {rv}')
    if rv > 0:
        return 1
    elif rv < 0:
        return -1
    else:
        return 0

def merge_sort(arr, callback):
    if len(arr) < 2:
        return arr

    mid = len(arr) // 2

    left_part, right_part = arr[:mid], arr[mid:]

    left_part = merge_sort(left_part, callback)
    right_part = merge_sort(right_part, callback)

    def merge(left_p, right_p, callback):
        res = []
              
        while len(left_p) > 0 and len(right_p) > 0:
            rv = callback(left_p[0], right_p[0])
            if rv == -1:
                res.append(left_p.pop(0))
            else: 
                res.append(right_p.pop(0))
                
        res.extend(left_p)
        res.extend(right_p)

        return res

    res = merge(left_part, right_part, callback)
    return res

def test_ints():
    passed_total = 0
    failed = []
    for _ in range(100):
        lst_length = randint(-1000, +1001)
        lst = []
        for i in range(lst_length):
            lst.append(randint(-1000, +1001))

        lst_merge_sorted = merge_sort(lst, int_compare)
        lst_std_sorted = sorted(lst)

        if lst_merge_sorted == lst_std_sorted:
            print(f"TEST {_} passed.")
            passed_total += 1
        else:
            print(f"TEST {_} failed.")
            print(f"\t lst: {lst}")
            failed.append(lst)

    print(f'\n\n\n Total passed: {passed_total}\n\n\n Total failed: {len(failed)}')


def main():
    test_ints()


if __name__ == "__main__":
    main()