Override globals in function imported from another module

Question

Let\'s say I have two modules:

a.py

value = 3
def x()
    return value

b.py

from          


        

Answer 1

I had the same problem. But then I remembered eval was a thing.
Here's a much shorter version(if you don't need arguments):
b.py:

from a import x as xx

# Define globals for the function here
glob = {'value': 4}
def x():
    return eval(xx.__code__, glob)

Hopefully after 2 years it'll still be helpful

Answer 2

So I found a way to (sort of) do this, although I don't think it entirely solves your problems. Using inspect, you can access the global variables of the file calling your function. So if you set up your files like so:

a.py

import inspect

value = 3

def a():
    return inspect.stack()[1][0].f_globals['value']

b.py

from a import a

value = 5

print(a())

The output is 5, instead of 3. However, if you imported both of these into a third file, it would look for the globals of the third file. Just wanted to share this snippet however.

Answer 3

I've come up with a solution through a mixture of guess-and-check and research. You can do pretty much exactly what I proposed in the question: copy a function object and replace its __globals__ attribute.

I am using Python 3, so here is a modified version of the answer to the question linked above, with an added option to override the globals:

import copy
import types
import functools

def copy_func(f, globals=None, module=None):
    """Based on https://stackoverflow.com/a/13503277/2988730 (@unutbu)"""
    if globals is None:
        globals = f.__globals__
    g = types.FunctionType(f.__code__, globals, name=f.__name__,
                           argdefs=f.__defaults__, closure=f.__closure__)
    g = functools.update_wrapper(g, f)
    if module is not None:
        g.__module__ = module
    g.__kwdefaults__ = copy.copy(f.__kwdefaults__)
    return g

b.py

from a import x
value = 4
x = copy_func(x, globals(), __name__)

The __globals__ attribute is read-only, which is why it must be passed to the constructor of FunctionType. The __globals__ reference of an existing function object can not be changed: Why is func.__globals__ documented as read-only?.