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Create your app with a function

Posted by Dan Jacob on 2010-05-25 @ 09:05 and filed in Application Structure

A useful pattern is creating your application using a function. This allows you to pass in different configuration settings, for example in unit tests.

For example:

from flask import Flask
from sqlalchemy import create_engine

from myapp import config
from myapp.views import frontend

def create_app(database_uri, debug=False):
    app = Flask(__name__)
    app.debug = debug

    # set up your database
    app.engine = create_engine(database_uri)

    # add your modules
    # other setup tasks

    return app

Then you can do this:

if __name__ == "__main__":
    app = create_app(config.DATABASE_URI, debug=True)

or in your unit tests:

import unittest

from myapp import config
from myapp import create_app

class TestCase(unittest.TestCase):
    def setUp(self):
        self.app = create_app(config.TEST_DATABASE_URI)
        self.client = self.app.test_client()

This snippet by Dan Jacob can be used freely for anything you like. Consider it public domain.