>>> parse_price('£16,000.00')
    16000.0
    >>> parse_price('-£16,000.00')
    -16000.0

def parse_price(price_string):
    """
    >>> parse_price('£16,000.00')
    16000.0
    >>> parse_price('-£16,000.00')
    -16000.0
    """
    return float(re.sub('[£,]', '', price_string))

    match = re.match('(?P<amount>-?£[\d,]+(\.\d{2})?)', price_string)
    if not match:
        raise ValueError("Charge not in format '(-)£16,000(.00)' : {}".format(
            repr(price_string)))
    return float(re.sub('[£,]', '', match.group('amount')))