Currency formatting in Python
New in 2.7
>>> '{:20,.2f}'.format(18446744073709551616.0)
'18,446,744,073,709,551,616.00'
http://docs.python.org/dev/whatsnew/2.7.html#pep-0378
See the locale module.
This does currency (and date) formatting.
>>> import locale
>>> locale.setlocale( locale.LC_ALL, '' )
'English_United States.1252'
>>> locale.currency( 188518982.18 )
'$188518982.18'
>>> locale.currency( 188518982.18, grouping=True )
'$188,518,982.18'