__init__.py 文件源码

def calc_checksum(self, data, checksum=0):
        '''
        Calculate the checksum for a given block of data, can also be used to
        update a checksum.

            >>> csum = modem.calc_checksum('hello')
            >>> csum = modem.calc_checksum('world', csum)
            >>> hex(csum)
            '0x3c'

        '''
        if platform.python_version_tuple() >= ('3', '0', '0'):
            return (sum(data) + checksum) % 256
        else:
            return (sum(map(ord, data)) + checksum) % 256