Improve registering blueprints in Flask application

app.py

from flask import Flask
from flask.ext.sqlalchemy import SQLAlchemy


class App(Flask):
    """
    Custom ``Flask`` class.
    """
    def register_blueprint(self, mixed, **kwargs):
        """
        Register blueprint to application and store all initialized extensions
        as ``blueprint.extensions`` attribute.
        """
        if isinstance(mixed, basestring):
            blueprint_name = '{}_blueprint'.format(mixed)
            module_name = 'appname.{}'.format(mixed)
            blueprint = import_string(module_name + ':' + blueprint_name)
        else:
            blueprint = mixed

        super(App, self).register_blueprint(blueprint, **kwargs)

        if not hasattr(blueprint, 'extensions'):
            setattr(blueprint, 'extensions', self.extensions)


# Initialize Flask application
app = App('appname')
app.config['SQLALCHEMY_SCHEMA_URI'] = 'sqlite:////tmp/appname.db'

# Initialize SQLAlchemy extension
db = SQLAlchemy(app)

# Register blueprint from ``appname.bluename``
app.register_blueprint('bluename')

# Register blueprint from ``appname.another_bluename`` and custom settings
app.register_blueprint('another_bluename', url_prefix='/another')