import re

__test__ = {}

re_digits_nondigits = re.compile(r'\d+|\D+')

__test__['re_digits_nondigits'] = r"""

    >>> re_digits_nondigits.findall('$1234.1234')
    ['$', '1234', '.', '1234']
    >>> re_digits_nondigits.findall('1234')
    ['1234']
    >>> re_digits_nondigits.findall('')
    []
    
"""

def FormatWithCommas(format, value):
    """

    >>> FormatWithCommas('%.4f', .1234)
    '0.1234'
    >>> FormatWithCommas('%i', 100)
    '100'
    >>> FormatWithCommas('%.4f', 234.5678)
    '234.5678'
    >>> FormatWithCommas('$%.4f', 234.5678)
    '$234.5678'
    >>> FormatWithCommas('%i', 1000)
    '1,000'
    >>> FormatWithCommas('%.4f', 1234.5678)
    '1,234.5678'
    >>> FormatWithCommas('$%.4f', 1234.5678)
    '$1,234.5678'
    >>> FormatWithCommas('%i', 1000000)
    '1,000,000'
    >>> FormatWithCommas('%.4f', 1234567.5678)
    '1,234,567.5678'
    >>> FormatWithCommas('$%.4f', 1234567.5678)
    '$1,234,567.5678'
    >>> FormatWithCommas('%i', -100)
    '-100'
    >>> FormatWithCommas('%.4f', -234.5678)
    '-234.5678'
    >>> FormatWithCommas('$%.4f', -234.5678)
    '$-234.5678'
    >>> FormatWithCommas('%i', -1000)
    '-1,000'
    >>> FormatWithCommas('%.4f', -1234.5678)
    '-1,234.5678'
    >>> FormatWithCommas('$%.4f', -1234.5678)
    '$-1,234.5678'
    >>> FormatWithCommas('%i', -1000000)
    '-1,000,000'
    >>> FormatWithCommas('%.4f', -1234567.5678)
    '-1,234,567.5678'
    >>> FormatWithCommas('$%.4f', -1234567.5678)
    '$-1,234,567.5678'
    
    """

    parts = re_digits_nondigits.findall(format % (value,))
    for i in xrange(len(parts)):
        s = parts[i]
        if s.isdigit():
            parts[i] = _commafy(s)
            break
    return ''.join(parts)
    
def _commafy(s):

    r = []
    for i, c in enumerate(reversed(s)):
        if i and (not (i % 3)):
            r.insert(0, ',')
        r.insert(0, c)
    return ''.join(r)