app.py

import os

APP_CHOICES = {
    "Default App": "simple_app",
    "Advanced App": "adv_app"
}

app_choice = os.getenv("APP_CHOICE", "simple_app")

if app_choice == "adv_app" and os.path.exists("adv_app.py"):
    from adv_app import *
else:
    from simple_app import *