Python integer base conversion (Quora answer)

base_convert.py

# A less abstract version fo this was created for
# quora answer https://qr.ae/psY5cy
import pytest
from numbers import Number


def base_convert(x: int, radix: int) -> str:
    symbols = '0123456789abcdefghijklmnopqrstuvwxyz'
    if radix < 2 or radix > len(symbols):
        raise ValueError(f"radix must be in [2, {len(symbols)}]")

    if not isinstance(x, Number):
        raise TypeError
    if not isinstance(x, int):
        raise NotImplementedError("Only handles int at the moment")

    # some special cases
    if x == 0:
        return "0"
    if x < 0:
        return '-' + base_convert(-x, radix)

    digits = []
    while x > 0:
        x, r = divmod(x, radix)
        digits.append(symbols[r])
    return ''.join(reversed(digits))


def base6(x: int) -> str:
    return base_convert(x, 6)


def test_base6() -> None:
    vectors = [
        (6, "10"),
        (0, "0"),
        (5, "5"),
        (35, "55"),
        (36, "100"),
        (37, "101"),
        (71, "155"),
        (-71, "-155"),
        (-0, "0"),
    ]

    for tv in vectors:
        input, expected = tv
        assert base6(input) == expected


if __name__ == '__main__':
    status = pytest.main([__file__])
    print(f'pytest status: {status}')