Flask + Injector - A dependency-injected web framework.

gistfile1.py

from injector import Module, inject, singleton
from flask import Flask, Request, jsonify
from flask.ext.cache import Cache
from flask.ext.injector import Builder, route, decorator
from flask.ext.sqlalchemy import SQLAlchemy
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm.exc import NoResultFound
from sqlalchemy import Column, String

"""
This is an example of using Injector (https://github.com/alecthomas/injector) and Flask.

Flask provides a lot of very nice features, but also requires a lot of globals
and tightly bound code. Flask-Injector seeks to remedy this.
"""


# Create an adapter for the Flask-Cache decorator.
cached = decorator(Cache.cached)

# We use standard SQLAlchemy models rather than the Flask-SQLAlchemy magic, as
# it requires a global Flask app object and SQLAlchemy db object.
Base = declarative_base()


class KeyValue(Base):
    __tablename__ = 'data'

    key = Column(String, primary_key=True)
    value = Column(String)

    def __init__(self, key, value):
        self.key = key
        self.value = value

    def serializable(self):
        return


@route('/api/store', methods=['GET'])
class KeyValueStore(object):
    @inject(db=SQLAlchemy, request=Request)
    def __init__(self, db, request):
        self.db = db
        self.request = request

    @route('/<key>')
    def get(self, key):
        try:
            kv = self.db.session.query(KeyValue).filter(KeyValue.key == key).one()
        except NoResultFound:
            response = jsonify(status='No such key', context=key)
            response.status = '404 Not Found'
            return response
        return jsonify(key=kv.key, value=kv.value)

    @cached(timeout=1)
    @route('/')
    def list(self):
        data = [i.key for i in self.db.session.query(KeyValue).order_by(KeyValue.key)]
        return jsonify(keys=data)

    @route('/', methods=['POST'])
    def create(self):
        kv = KeyValue(self.request.form['key'], self.request.form['value'])
        self.db.session.add(kv)
        self.db.session.commit()
        response = jsonify(status='OK')
        response.status = '201 CREATED'
        return response

    @route('/<key>', methods=['DELETE'])
    def delete(self, key):
        self.db.session.query(KeyValue).filter(KeyValue.key == key).delete()
        self.db.session.commit()
        response = jsonify(status='OK')
        response.status = '200 OK'
        return response


class AppModule(Module):
    """Configure the application."""
    def configure(self, binder):
        app = binder.injector.get(Flask)
        # We configure the DB here, explicitly, as Flask-SQLAlchemy requires
        # the DB to be configured before request handlers are called.
        db = self.configure_db(app)
        binder.bind(SQLAlchemy, to=db, scope=singleton)
        binder.bind(Cache, to=Cache(app), scope=singleton)

    def configure_db(self, app):
        db = SQLAlchemy(app)
        Base.metadata.create_all(db.engine)
        db.session.add_all([
            KeyValue('hello', 'world'),
            KeyValue('goodbye', 'cruel world'),
        ])
        db.session.commit()
        return db


def main():
    builder = Builder([KeyValueStore], [AppModule()], config=dict(
        DB_CONNECTION_STRING=':memory:',
        CACHE_TYPE='simple',
        SQLALCHEMY_DATABASE_URI='sqlite://',
    ))
    app = builder.build()
    app.debug = True
    # app.run()
    client = app.test_client()

    response = client.get('/api/store/')
    print('%s\n%s%s' % (response.status, response.headers, response.data))
    response = client.post('/api/store/', data={'key': 'foo', 'value': 'bar'})
    print('%s\n%s%s' % (response.status, response.headers, response.data))
    response = client.get('/api/store/')
    print('%s\n%s%s' % (response.status, response.headers, response.data))
    response = client.get('/api/store/hello')
    print('%s\n%s%s' % (response.status, response.headers, response.data))
    response = client.delete('/api/store/hello')
    print('%s\n%s%s' % (response.status, response.headers, response.data))
    response = client.get('/api/store/')
    print('%s\n%s%s' % (response.status, response.headers, response.data))
    response = client.get('/api/store/hello')
    print('%s\n%s%s' % (response.status, response.headers, response.data))
    response = client.delete('/api/store/hello')
    print('%s\n%s%s' % (response.status, response.headers, response.data))


if __name__ == '__main__':
    main()

For anyone finding this these days: Flask-Injector (https://github.com/alecthomas/flask_injector) and Injector (https://github.com/alecthomas/injector) are the current repositories for the Python dependency injection framework itself and the Flask integration.