Flask is a Python web application micro-framework built on top of the Werkzeug WSGI library. Flask may be "micro", but it’s ready for production use on a variety of needs.
The "micro" in micro-framework means Flask aims to keep the core simple but extensible. Flask won’t make many decisions for you, such as what database to use, and the decisions that it does make are easy to change. Everything is up to you, so that Flask can be everything you need and nothing you don't.
The community supports a rich ecosystem of extensions to make your application more powerful and even easier to develop. As your project grows you are free to make the design decisions appropriate for your requirements.
Flask supports signals using Blinker. Signal support is optional; they will only be enabled if Blinker is installed.
pip install blinker
http://flask.pocoo.org/docs/dev/signals/
Signals are not asynchronous. When a signal is sent, it immediately executes each of the connected functions sequentially.
Sessions are derived from dictionaries which means they will work with most common dictionary methods.
The location parameter must be a URL. It can be input raw, such as 'http://www.webpage.com' or it can be built with the url_for() function.