from smbus import SMBus

class PCF8574(object):
    def __init__(self, bus, addr):
        self.__addr = addr
        self.__bus = SMBus(bus)

    def __enter__(self):
        return self

    def __exit__(self, exc_type, exc_value, traceback):
        self.__bus.close()

    def read(self):
        return ~self.__bus.read_byte(self.__addr)

    def write(self, value):
        self.__bus.write_byte(self.__addr, ~value)