Hi everyone.

I'd like to use pygad's parallel_processing feature to enable parallelization with multiprocessing like that:

parallel_processing=["process", 2]

Then I have my fitness function which is a closure which has access to its outer function variables and meets pygad's requirement to have only 2 arguments at the same time like this:

def do_recognize(img):
 def inner(inp, _):
 best_fitness, _ = scan(img, inp, debug=False)
 return best_fitness
 return inner

When I try to use approach from above example I'm getting an error that it is impossible to pickle inner function:

AttributeError: Can't pickle local object 'do_recognize.<locals>.inner

Ok, my next attempt is to use functools.partial like this:

fitness = partial(do_recognize, img)

But this doesn't work too, because of pygad's check that fitness function has exactly 2 arguments which it does by using __code__co_argcount property which seems to be absent for partial return type.

I came up with the following ugly hack:

 Dummy = namedtuple('Dummy', 'co_argcount')
 find_board = partial(do_recognize, img)
 find_board.__code__ = Dummy(co_argcount=2)

this perfectly satisfies both multiprocessing and pygad but it doesn't look cool at all.

I'd like to propose to avoid using __code__co_argcount function for arity check and switch to something less unusual.
For example inspect package could be helpful:

import inspect
assert len(inspect.getargspec(f).args) == 2

which at least works perfectly fine with partial.