"""
Demonstrate a problem with user-defined exceptions raised
during unpickling that cPickle tries to extend with additional
exception information
"""

import cPickle as pickler
import logging


class MyException(Exception):
    """Exception class with restrictive __init__ arguments"""
    def __init__(self, message):
        self.message = message

    def __str__(self):
        return self.message


class BadReduce(object):
    """Object that raises an exception on unpickling"""
    def __init__(self, arg):
        if arg == 1123:
            exception = MyException('BadReduce init failed')
            # Demonstrate that we successfully constructed the exception
            logging.info('Raising exception "%s"', exception)
            raise exception

    def __reduce__(self):
        return BadReduce, (1123,), None, None, None


def main():
    logging.basicConfig(level=logging.NOTSET)
    logging.info('Creating BadReduce object')
    b1 = BadReduce(0)
    logging.info('Pickling')
    s1 = pickler.dumps(b1, pickler.HIGHEST_PROTOCOL)
    logging.info('Unpickling')
    try:
        pickler.loads(s1)
    except MyException as e:
        logging.info('Got MyException "%s"', e)
    logging.info('Done')


if __name__ == '__main__':
    main()