Someone on fr.comp.lang.python asked for a way to format a float as a french currency (i.e. with thousands separator). There doesn't seem to be anything available in the standard library and the % operator has no specific format for currency. Here's the code I came up with:

def as_currency(amount, thousand_sep=' ', decimal_sep=',', symbol='¤'):
    num = '%.2f'%amount
    left, right = num.split('.')
    left_digits = list(left)
    spaced_digits = [decimal_sep, right, symbol ]
    while left_digits:
        spaced_digits = [thousand_sep] + left_digits[-3:] + spaced_digits
        del left_digits[-3:]
    return ''.join(spaced_digits[1:])

This could probably be enhanced by using the locale module to get the values. It's rather unfortunate that locale.format has not % substitution for currencies.