How would I make my Python game Moddable?

Haha. Solved my own problem in less than 10 minutes.

So what I really wanted to do was to make a simple game modifiable.

So I created this (not necessarily smart or safe) method of making a configuration file that could be used for "modding".

This is what it looks like:

# main.py
import turtle as t
screen = t.Screen()
turt = t.Turtle()
cfg = open("mods.py","r")
cfg = cfg.read()
cfg = cfg.split("\n")
for i in range(len(cfg)):
    if i < len(cfg):
            exec(cfg[i])

for i in range(8):
    turt.forward(100)
    turt.right(45)
    turt.backward(75)
screen.exitonclick()

and in mods.py:

turt = t.Turtle()
turt.color("red")

Now before everyone gets all up in my face for using exec, let me just say that for a solution that was thought of quickly, I am okay with it. Plus, it wouldn't be that hard to add some sort of portection, ie if "os" not in cfg[i]: exec(cfg[i]) and all of that would really just be a matter of time consumption.

I had to add if i <len(cfg): because when I split at the \n that was adding a blank element at the end of the list it generated. I doubt that would raise an error, but no harm in being a little extra cautious.

Overall, I'm glad with my solution... I'll add security detection and stuff but as of right now it will work, because the game I am working on will not be a public game.

Even if we're OK with the approach being totally unsafe, OP's answer still doesn't offer a sensible solution, since loops and functions, or anything multi-line can't be used in the mods file, and the mods file has to know about the existence of certain magic globals like t.

Here's a solution that lets you run a fully legitimate Python file. Note that this is completely unsafe and not suitable in any sort of public environment.

main.py:

import importlib.util
import pathlib
from turtle import Screen, Turtle

mods_path = pathlib.Path("mods.py")
spec = importlib.util.spec_from_file_location("mods", mods_path)
mods = importlib.util.module_from_spec(spec)
spec.loader.exec_module(mods)

turt = Turtle()
turt.color("green")

for _ in range(5):
    turt.forward(40)
    turt.left(46)

Screen().exitonclick()

mods.py:

from turtle import Screen, Turtle

t = Turtle()
t.color("red")
t.pensize(3)
Screen().bgcolor("black")

for _ in range(5):
    t.forward(50)
    t.right(26)

The turtle module is basically a global singleton, which facilitates this nicely. All drawing will occur on the same window. You can expose variables to the module from main.py if desired, via mods.t = t, in OP's example.