documentation.py

def countdown(start):
    """ creates a list of numbers from start to zero

    :param start: (int) the starting value
    :return: the list of numbers
    :rtype: list
    :raises ValueError: if start is less than 1

    Example:
        countdown(start=3) >>> [3, 2, 1 0]

    """
    if start < 1:
        raise ValueError('start must not be less than 1')
    current = start
    numbers = []
    while current >= 0:
        numbers.append(current)
        current -= 1
    return numbers

countdown(start=3)