Flask: are blueprints necessary for app factories?

You surely can have application factory without the blueprint, but that often makes no sense.

Assuming you have an application package called myapp. Here is your __init__.py:

from flask import Flask

def create_app():
    app = Flask(__name__)

    return app

Now we create a new .py file called autoapp.py （or wsgi.py or manage.py etc.） outside of myapp package. In the autoapp.py, you create the application instance and import the views from myapp:

from myapp import create_app

app = create_app()

from myapp import views

The import statement will link the app with your routes. You can import app in your views.py like this:

from autoapp import app

@app.route('/')
def index():
    return 'Hello!'

The application structure:

myapp/
    myapp/
        __init__.py
        views.py
    autoapp.py

For those who googled this question. You don't have to use blueprints. Just import current_app as app in your routes.py (or views.py, whatever) and you are free to go.

from flask import current_app as app

Also, you have to add this to the factory (the create_app function) to register your routes:

with app.app_context():
    from . import routes

technically, you don't need blueprints, you can just register each route on your create_app function. Generally speaking that's not a great idea, and it's kind of why blueprints exist.

Example without blueprints

def create_app():
  app = Flask(__name__)

  @app.route('/')
  def index():
    return render_template('index.html')

  return app

You can have a single app factory for both testing and whatever else if you configure it that way. If you want to load different blueprints based on if it is in testing, you can do something like this.

from project.config import configurations as c

def create_app(config=None):
  " make the app "
  app = Flask(__name__)
  app.config.from_object(c.get(config, None) or c['default'])

  configure_blueprints(app)

  return app

def configure_blueprints(app):
  " register the blueprints on your app "
  if app.testing:
    from project.test_bp import bp
    app.register_blueprint(bp)
  else:
    from project.not_test_bp import bp
    app.register_blueprint(bp)

then project/config.py could be like this:

class DefaultConfig(object):
  PROJECT_NAME = 'my project'

class TestingConfig(DefaultConfig):
  TESTING = True

class DevConfig(DefaultConfig):
  DEBUG = True

configurations = {
  'testing': TestingConfig,
  'dev': DevConfig,
  'default': DefaultConfig
}

Make a folder for each blueprint where the __init__.py in the folder instantiates the blueprint. Let's say for a blueprint called routes

from flask import Blueprint

bp = Blueprint('routes', __name__)

from project.routes import views

then in project/routes/views.py, you can put your views.

from project.routes import bp

@bp.route('/')
def index():
  return render_template('routes/index.html')