number_format.py

from decimal import Decimal


def number_format(value, decimal_separator=',', mille_separator=None, significance=2):
    """Format a integer or decimal number like PHP number_format function.

    Args:
        value: The value to be formatted. If its not a valid number, ValueError
            will be rised
        decimal_separator: The string to use to split decimal places
        mille_separator: If specified, milles will be splitted with this string
        significance: Number of decimal places

    Returns:
        A string with the value formatted

    Raises:
        ValueError: If `value` is not a valid number
    """        
    if not type(value) in [int, float, Decimal]:
        try:
            value = float(value)
        except ValueError:
            raise ValueError('%s is not a number' % value)

    # convert to string
    format_string = '.%df' % significance
    value = format(value, format_string)

    # split decimal part
    integer, decimal = value.split('.')

    if mille_separator:
        final_value = []
        # add mille_separator to integer part (reverse integer part slicing string)
        count = 0
        for number in integer[::-1]:
            if count > 0 and count % 3 == 0:
                final_value.append(mille_separator)
            final_value.append(number)
            count += 1
        final_value = ''.join(reversed(final_value))
    else:
        final_value = integer

    return '%s%s%s' % (final_value, decimal_separator, decimal)