When to use Tornado, when to use Twisted / Cyclone / GEvent / other
Which of these frameworks / libraries would be the best choise for building modern multiuser web application? I would love to have an asynchronous webserver which will allow me to scale easly. What solution will give the best performance / scalability / most useful framework (in terms of easy of use and easy of developing)?
It would be great if it will provide good functionality (websockets, rpc, streaming, etc).
What are the pros and cons of each solution?
Answer
"Django is a high-level Python Web framework that encourages rapid development and clean, pragmatic design". If you are building something that is similar to a e-commerce site, then you should probably go with Django. It will get your work done quick. You dont have to worry about too many technology choices. It provides everything thing you need from template engine to ORM. It will be slightly opinionated about the way you structure your app, which is good If you ask me. And it has the strongest community of all the other libraries, which means easy help is available.
"Flask is a microframework for Python based on Werkzeug, Jinja 2 and good intentions". Beware - "microframework" may be misleading. This does not mean that Flask is a half-baked library. This mean the core of flask is very, very simple. Unlike Django, It will not make any Technology decisions for you. You are free to choose any template engine or ORM that pleases you. Even though it comes with Jinja template engine by default, you are always free to choose our own. As far as I know Flask comes in handy for writing APIs endpoints (RESTful services).
"Twisted is an event-driven networking engine written in python". This is a high-performance engine. The main reason for its speed is something called as deferred. Twisted is built on top of deferreds. For those of you who dont know about defereds, it is the mechanism through with asynchronous architecture is achieved. Twisted is very fast. But is not suitable for writing conventional webapps. If you want to do something low-level networking stuff, twisted is your friend.
"Tornado is a Python web framework and asynchronous networking library, originally developed at FriendFeed. By using non-blocking network I/O, Tornado can scale to tens of thousands of open connections, making it ideal for long polling, WebSockets, and other applications that require a long-lived connection to each user". Tornado stands some where between Django and Flask. If you want to write something with Django or Flask, but if you need a better performance, you can opt for Tornado. it can handle C10k problem very well if it is architected right.
"Cyclone is a web server framework for Python that implements the Tornado API as a Twisted protocol". Now, what if you want something that is nearly as performant as Twisted but easy to write conventional webapps? Say hello to cyclone. I would prefer Cyclone over Tornado. It has an API that is very similar to Tornado. As a matter of fact, this is a fork of Tornado. But the problem is it has relativly small community. Alexandre Fiori is the only main commiter to the repo.
"Pyramid is a general, open source, Python web application development framework. Its primary goal is to make it easier for a Python developer to create web applications." I haven't really used Pyramid, but I went through the documentation. From what I understand, Pyramid is very similar to Flask and I think you can use Pyramid wherever Flask seems appropriate and vice-versa.
EDIT: Request to review any other frameworks are welcomed!