Question

I have a flask application that is laid out as a few MethodViews.

On one of my MethodViews, I want to open a database connection before each request, and close it after the request, very similar to this.

I know how to use global @app.before_request and @app.teardown_request functions, but those will run for every single request. I want limited versions that will only run for the routes in a particular MethodView.

Answer 1

You could use a decorator, that would tag certain views as database dependent.

NoSQLStore = {}

class NoSQL(object):
    """ fake """
    def query(self, key): 
        return '%s\n' % NoSQLStore.get(key, 'no such key')
    def put(self, key, value):
        NoSQLStore[key] = value

def with_database(fn):
    """ Decorator for functions, that need database access.
        NoSQL object will be stored under ``g.db``. 
    """
    def connect_and_close(*args, **kwargs):
        g.db = NoSQL()
        __result = fn(*args, **kwargs)
        # a real database should be somehow ``closed()`` here
        return __result
    return connect_and_close

class StoreAPI(MethodView):

    @with_database
    def get(self):
        return g.db.query(request.args.get('key'))

    @with_database
    def post(self):
        key, value = str(random.randint(0, 1000)), str(random.randint(0, 1000))
        g.db.put(key, value)
        return 'set %s => %s\n' % (key, value)

A runnable standalone example can be found here: https://gist.github.com/4424587