How to unpickle an object whose class exists in a different namespace (python)?

Question

If I have a script that defines a class:

script = \"\"\"

class myClass:
    def __init__(self):
        self.name = \'apple\'
        self.color = \'green\'         


        

Answer 1

I discovered a solution this. It seems the problem is executing code in a dict prevents python from figuring out where the class is defined. The solution is to create an empty module, execute the code in the module, and then add the module to sys.modules so python knows about it.

script = """
class myClass:
    def __init__(self):
        self.name = 'apple'
        self.color = 'green'
"""

import imp, sys

moduleName = 'custom'

module = imp.new_module(moduleName)

exec script in module.__dict__

sys.modules[moduleName] = module

Now it is possible to pickle and unpickle an instance of the class:

import pickle
a = module.myClass()
s = pickle.dumps(a)
b = pickle.loads(s)