python - How to pickle a ssl.SSLContext object

Question

Python 3.5 on windows, try these:

import ssl, pickle, multiprocessing
context = ssl.create_default_context()
foo = pickle.dumps(context)
pickle.loads(foo)

Throws an exception:

TypeError: __new__() missing 1 required positional argument: 'protocol'

subclass of multiprocessing.Process throws the same exception:

class Foo(multiprocessing.Process):
    def __init__(self):
        super().__init__()
        self.context = ssl.create_default_context()

    def run(self):
        pass

if __name__ == '__main__':
    foo = Foo()
    foo.start()

Answer 1

Something like this should work:

>>> import pickle, copyreg, ssl
>>>
>>> def save_sslcontext(obj):
...   return obj.__class__, (obj.protocol,)
... 
>>> copyreg.pickle(ssl.SSLContext, save_sslcontext)
>>> 
>>> context = ssl.create_default_context()
>>> foo = pickle.dumps(context)
>>> _foo = pickle.loads(foo)
>>> _foo
<ssl.SSLContext object at 0x1011812a8>
>>> _foo.protocol
2
>>> 

Basically, a SSLContext needs a protocol, and for whatever reason, the protocol is not saved (e.g. it's not in a __reduce__ method) when the instance is pickled. If you need more state (i.e. other args and kwds from the __init__ method), then you'll need to extend the return value from the save_sslcontext function above. (Note, if you are in python 2.x, then the appropriate module is copy_reg).