Exponent function with recursion

power.py

import pytest


def power(a, n):
    """
    power(base, exponent)

    Returns  the result of raising base to the power exponent.

    Parameters:
    a (int): The number to be multiplied exponent times
    b (int): The non-negative exponent. A ValueError is thrown if b is negative

    Returns:
    int: a raised to the power b.
    """

    if n < 0:
        raise ValueError("second parameter should be non-negative")

    if n == 0:
        return 1
    return a * power(a, n - 1)


def test_exponent_zero():
    assert power(459, 0) == 1


def test_negative_exponent():
    with pytest.raises(ValueError) as excinfo:
        power(456, -1)
    assert "non-negative" in str(excinfo.value)


def test_one_exponent_any_number_is_one():
    assert power(1, 435) == 1


def test_a_exponent_one_is_a():
    a = 456
    assert power(a, 1) == a


def test_same_result_as_builtin_power():
    assert power(2, 45) == 2**45

Requires pytest. Run tests with

pytest power.py