"""
 average.py

 This is an in class example of functions

"""

def sum_list(numbers=[]):
    """ Return the sum of a list of numbers. 
        >>> sum_list([3, 15, 4])
        22
    """
    result = 0
    for n in numbers:
        result = result + n
    return result

def average(numbers=[]):
    """ Return the average of a list of numbers. 
        >>> average([1,2])
        1.5
        >>> average()
        0
    """
    return float(sum_list(numbers)) / len(numbers)


if __name__ == '__main__':
    import doctest
    doctest.testmod()