bjjclover_num_format_ex.py

def number_groupings(number):
    """Given an integer, return a string representation of that integer
    with ',' at the appropriate groupings to indicate thousands places.

    >>> number_groupings(1234)
    '1,234'

    >>> number_groupings(12345678)
    '12,345,678'

    >>> number_groupings(-12345)
    '-12,345'
    """

    strnumber = str(number)
    start = len(strnumber)%3

    if start == 0:
        numstring = strnumber[0:3]
        start = 3

    else:
        numstring = strnumber[0:start]

    for i in range(start, len(strnumber), 3):
        numstring += ',' + strnumber[i:i+3]

    return numstring