Handling the classmethod pickling issue with copy_reg

Question

I met a pickling error when dealing with multiprocessing:

 from multiprocessing import Pool

 def test_func(x):
     return x**2

 class Test:
     @classmethod
         


        

Answer 1

Instead of returning the actual class object from _pickle_method, return a string that can be used to import it when unpickling and then do that in _unpickle_method