You’re given a string of characters that are only 2s and 0s. Return the index of the first occurrence of “2020” without using the indexOf (or similar) function, and -1 if it’s not found in the string.

find_2020.py

def find(s: str) -> int:
    if not isinstance(s, str) or not all(c in {'2', '0'} for c in s):
        return -1

    i = 0
    while i < len(s):
        if s[i:i + 4] == '2020':
            return i
        i += 1
    return -1


def test_example():
    assert find('2220000202220020200') == 14


def test_not_found():
    assert find('2220000202220020220') == -1


def test_bad_inputs():
    assert find(2020) == -1
    assert find('123452020') == -1


if __name__ == '__main__':
    test_example()
    test_not_found()
    test_bad_inputs()