Best way to pass a config object between modules?

For the "canonical" solution, turn Config into a function that creates the config object in a global variable.

import threading
config = None
congiglock = threading.Lock()
def Config(...):
    global config
    with configlock.lock():
        if config:
            raise Error()
    config = _Config(...)

Programmers no longer instantiate the configuration object, so it can be renamed.

Consumers would use the config variable via its module

import pkg.config
def action():
    if pkg.config.config.foo:
        print("bar")

You could move the function to the package init for less typing. But you shouldn't from pkg.config import config because you might get the None before config really happened.