Flask: How to manage different environment databases?

I am working on an app which looks similar to

facebook/
         __init__.py
         feed/
             __init__.py
             business.py
             views.py
             models/
                    persistence.py
                    user.py
         chat/
             __init__.py
             models.py
             business.py
             views.py
         config/
                dev.py
                test.py
                prod.py 

I want to have three environments Dev, Test and Production.
I have the following requirements:
a.) When I start the server python runserver.py, I would like to mention which environment I want to connect - Dev, Test or Production.
b.) Dev & Production should have the schema built and just need to connect to machine
c.) I would also like for my test to connect to sqlite db, and create the schema, run tests

How can I achieve this in a configuration manner so that I do not have to hardcode anything related to database.

Are there any good patterns available in flask?

Currently my runerver.py has hardcoding for environment that I don't like,

app = Flask(__name__)
app.config['SECRET_KEY'] = dev.SECRET_KEY

I am looking for better ideas than I have