Serialize a Python method with global variables by dill

Question

Here's an example code where FLAG is a global variable. The method A.func is a blackbox to me so that I don't know it calls FLAG before serialization.

import dill as pickle
FLAG = 100

class A:
  def func(self):
    print FLAG * 10

a = A()
dump = pickle.dumps(a.func)
del FLAG
foo = pickle.loads(dump) <-- fail here "NameError: global name 'FLAG' is not defined"
foo()

In related questions:

• Serialize a python function with dependencies
• How to pickle a python function with its dependencies?

The most practical solution is using cloudpickle. But it seems that dill is more robust than cloudpickle. So I'd like to stick to dill or other mature picklers.

I don't mind to modify some dill code by myself if necessary.

Thanks for any help in advance :)

Answer 1

I'm the dill author. It works if you use the recurse setting, which handles globals very similarly to how cloudpickle handles globals.

>>> import dill
>>> FLAG = 100
>>> 
>>> class A:
...   def func(self):
...     return FLAG*10
... 
>>> a = A()
>>> dump = dill.dumps(a.func, recurse=True)
>>> del FLAG
>>> foo = dill.loads(dump)
>>> foo()
1000
>>> 

dill provides several settings, that give you serialization variants. If you want to always use this setting, then you can do this:

>>> dill.settings['recurse'] = True