How to make a custom exception class with multiple init args pickleable

Question

Why does my custom Exception class below not serialize/unserialize correctly using the pickle module?

import pickle

class MyException(Exception):
    def __ini         


        

Answer 1

I like Martijn's answer, but I think a better way is to pass all arguments to the Exception base class:

class MyException(Exception):
    def __init__(self, arg1, arg2):
        super(MyException, self).__init__(arg1, arg2)        
        self.arg1 = arg1
        self.arg2 = arg2

The base Exception class' __reduce__ method will include all the args. By not making all of the extra arguments optional, you can ensure that the exception is constructed correctly.