Less than 4B if statements

def is_even_like_a_human(number):
    return str(number)[-1] in {"0", "2", "4", "6", "8"}


def is_even_like_a_computer(number):
    return (number & 1) == 0


def is_even_like_a_lisp_programmer(number):
    if number == 0:
        return True
    elif number == 1:
        return False
    else:
        return is_even_like_a_lisp_programmer(number - 2)


def is_even_by_cheating_on_a_modulo_operator(number):
    return (number // 2) * 2 == number


def is_even_like_its_100BC(number):
    if number == 0:
        raise ValueError("0 non est numerus, smarty braccas")

    def int_to_roman(num):
        symbols = [
            "M",
            "CM",
            "D",
            "CD",
            "C",
            "XC",
            "L",
            "XL",
            "X",
            "IX",
            "V",
            "IV",
            "I",
        ]
        values = [1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1]
        roman = ""
        for i in range(len(symbols)):
            while num >= values[i]:
                roman += symbols[i]
                num -= values[i]
        return roman

    roman = int_to_roman(number)

    if roman.endswith("X") and not roman.endswith("IX"):
        return True
    elif roman.endswith("IX"):
        return False
    elif roman.endswith("VIII"):
        return True
    elif roman.endswith("VII"):
        return False
    elif roman.endswith("VI"):
        return True
    elif roman.endswith("V") and not roman.endswith("IV"):
        return False
    elif roman.endswith("IV"):
        return True
    elif roman.endswith("III"):
        return False
    elif roman.endswith("II"):
        return True
    elif roman.endswith("I"):
        return False
    else:
        return True


def is_even_like_its_1800(number):
    morse_numerals = [
        "-----",
        ".----",
        "..---",
        "...--",
        "....-",
        ".....",
        "-....",
        "--...",
        "---..",
        "----.",
    ]
    # it is a pity to convert an entire number, but we need to be thorough:
    morse_code = "".join([morse_numerals[int(digit)] for digit in str(number)])
    dots_count = morse_code[-5:].count(".")
    # build on top of the past experience:
    # (also, yes, in 1800 zero is a known number)
    return dots_count == 0 or is_even_like_its_100BC(dots_count)


def is_even_in_sudoku(number):
    sudoku = [
        [1, 2, 3],
        [4, 5, 6],
        [7, 8, 9]
    ]
    d = str(number)[-1]  # sudokuizes a number
    for i in range(3):
        for j in range(3):
            if sudoku[i][j] == int(d):
                return not is_even_like_a_human(i + j)
    return True  # digits off the grid get a benefit of the doubt


#
# Tests:
# TODO: Figure out how to use the A. Karlsson's performance-optimized version for tests
#


def test_is_even(is_even_fn):
    try:
        assert is_even_fn(0), "0 is even!"
    except ValueError as e:
        print(e)
    assert not is_even_fn(1), "1 is odd!"
    assert is_even_fn(2), "2 is even!"
    assert not is_even_fn(3), "3 is odd!"
    assert is_even_fn(4), "4 is even!"
    assert not is_even_fn(5), "5 is odd!"
    assert is_even_fn(6), "6 is even!"
    assert not is_even_fn(7), "7 is odd!"
    assert is_even_fn(8), "8 is even!"
    assert not is_even_fn(9), "9 is odd!"
    assert is_even_fn(10), "10 is even!"
    assert not is_even_fn(11), "11 is odd!"
    assert is_even_fn(12), "12 is even!"
    assert not is_even_fn(13), "13 is odd!"
    assert is_even_fn(14), "14 is even!"
    assert not is_even_fn(15), "15 is odd!"
    assert is_even_fn(16), "16 is even!"
    assert not is_even_fn(17), "17 is odd!"
    assert is_even_fn(18), "18 is even!"
    assert not is_even_fn(19), "19 is odd!"
    assert is_even_fn(20), "20 is even!"
    assert not is_even_fn(21), "21 is odd!"
    assert is_even_fn(22), "22 is even!"
    assert not is_even_fn(23), "23 is odd!"
    assert is_even_fn(24), "24 is even!"
    assert not is_even_fn(25), "25 is odd!"
    assert is_even_fn(26), "26 is even!"
    assert not is_even_fn(27), "27 is odd!"
    assert is_even_fn(28), "28 is even!"
    assert not is_even_fn(29), "29 is odd!"
    assert is_even_fn(30), "30 is even!"
    assert not is_even_fn(31), "31 is odd!"
    assert is_even_fn(32), "32 is even!"
    assert not is_even_fn(33), "33 is odd!"
    assert is_even_fn(34), "34 is even!"
    assert not is_even_fn(35), "35 is odd!"
    assert is_even_fn(36), "36 is even!"
    assert not is_even_fn(37), "37 is odd!"
    assert is_even_fn(38), "38 is even!"
    assert not is_even_fn(39), "39 is odd!"
    assert is_even_fn(40), "40 is even!"
    assert not is_even_fn(41), "41 is odd!"
    assert is_even_fn(42), "42 is even!"
    assert not is_even_fn(43), "43 is odd!"
    assert is_even_fn(44), "44 is even!"
    assert not is_even_fn(45), "45 is odd!"
    assert is_even_fn(46), "46 is even!"
    assert not is_even_fn(47), "47 is odd!"
    assert is_even_fn(48), "48 is even!"
    assert not is_even_fn(49), "49 is odd!"
    assert is_even_fn(50), "50 is even!"
    assert not is_even_fn(51), "51 is odd!"
    assert is_even_fn(52), "52 is even!"
    assert not is_even_fn(53), "53 is odd!"
    assert is_even_fn(54), "54 is even!"
    assert not is_even_fn(55), "55 is odd!"
    assert is_even_fn(56), "56 is even!"
    assert not is_even_fn(57), "57 is odd!"
    assert is_even_fn(58), "58 is even!"
    assert not is_even_fn(59), "59 is odd!"
    assert is_even_fn(60), "60 is even!"
    assert not is_even_fn(61), "61 is odd!"
    assert is_even_fn(62), "62 is even!"
    assert not is_even_fn(63), "63 is odd!"
    assert is_even_fn(64), "64 is even!"
    assert not is_even_fn(65), "65 is odd!"
    assert is_even_fn(66), "66 is even!"
    assert not is_even_fn(67), "67 is odd!"
    assert is_even_fn(68), "68 is even!"
    assert not is_even_fn(69), "69 is odd!"
    assert is_even_fn(70), "70 is even!"
    assert not is_even_fn(71), "71 is odd!"
    assert is_even_fn(72), "72 is even!"
    assert not is_even_fn(73), "73 is odd!"
    assert is_even_fn(74), "74 is even!"
    assert not is_even_fn(75), "75 is odd!"
    assert is_even_fn(76), "76 is even!"
    assert not is_even_fn(77), "77 is odd!"
    assert is_even_fn(78), "78 is even!"
    assert not is_even_fn(79), "79 is odd!"
    assert is_even_fn(80), "80 is even!"
    assert not is_even_fn(81), "81 is odd!"
    assert is_even_fn(82), "82 is even!"
    assert not is_even_fn(83), "83 is odd!"
    assert is_even_fn(84), "84 is even!"
    assert not is_even_fn(85), "85 is odd!"
    assert is_even_fn(86), "86 is even!"
    assert not is_even_fn(87), "87 is odd!"
    assert is_even_fn(88), "88 is even!"
    assert not is_even_fn(89), "89 is odd!"
    assert is_even_fn(90), "90 is even!"
    assert not is_even_fn(91), "91 is odd!"
    assert is_even_fn(92), "92 is even!"
    assert not is_even_fn(93), "93 is odd!"
    assert is_even_fn(94), "94 is even!"
    assert not is_even_fn(95), "95 is odd!"
    assert is_even_fn(96), "96 is even!"
    assert not is_even_fn(97), "97 is odd!"
    assert is_even_fn(98), "98 is even!"
    assert not is_even_fn(99), "99 is odd!"
    assert is_even_fn(100), "100 is even!"


def main():
    is_even_or_add_fns = [
        globals()[name] for name in globals() if name.startswith("is_even_")
    ]

    for fn in is_even_or_add_fns:
        try:
            test_is_even(fn)
        except AssertionError as e:
            print(f"{fn.__name__} - FAIL ({e})")
        else:
            print(f"{fn.__name__} - OK")


if __name__ == "__main__":
    main()