ordinal.py

import pytest


suffixes = {
    '1': 'st',
    '2': 'nd',
    '3': 'rd',
}


def ordinal(n):
    s = str(n)
    if len(s) > 1 and s[-2] == '1':
        return f'{n}th'
    return f'{n}{suffixes.get(s[-1], "th")}'


@pytest.mark.parametrize('n, o', [
    (0, '0th'),
    (1, '1st'),
    (2, '2nd'),
    (3, '3rd'),
    (4, '4th'),
    (10, '10th'),
    (11, '11th'),
    (12, '12th'),
    (13, '13th'),
    (100, '100th'),
    (101, '101st'),
    (102, '102nd'),
    (103, '103rd'),
    (110, '110th'),
    (111, '111th'),
    (112, '112th'),
    (113, '113th'),
])
def test_ordinal(n, o):
    assert ordinal(n) == o