Cross module variable sharing without duplicating imports

Question

I have a module models.py with some data logic:

db = PostgresqlDatabase(database='database', user='user')

# models logic

and flask app which actually interacts with database:

from models import db, User, ...

But I want to move initializing all setting from one config file in flask app:

So I could separate importing db from other stuff (I need this for access to module variable db in models ):

import models
from models import User, ...
app.config.from_object(os.environ['APP_SETTINGS'])
models.db = PostgresqlDatabase(database=app.config['db'],
                               user=app.config['db'])

and use further db as models.db

But seems it is kinda ugly. Duplicating imports, different usage of module stuff..

Is there any better way how to handle this situation?

Answer 1

I'd recommend 1 level of indirection, so that your code becomes like this:

import const
import runtime

def foo():
    runtime.db.execute("SELECT ... LIMIT ?", (..., const.MAX_ROWS))

You get:

• clear separation of leaf module const
• mocking and/or reloading is possible
• uniform and concise access in all user modules

To get rich API on runtime , use the "replace module with object at import" trick ( see __getattr__ on a module )