Python Web Frameworks – Development Server | Hacker News Reader

Python Web Frameworks – Development Server

pyrseas.wordpress.com

44 pointsdabent20 comments

FYI, Quixote (http://quixote.ca) provides a bunch of options too:

     python -m quixote.server.simple_server
     python -m quixote.server.medusa_server
     python -m quixote.server.twisted_server
     python -m quixote.server.fastcgi_server
     python -m quixote.server.scgi_server

simple_server uses BaseHTTPServer and is thus single-threaded and blocking but works fine for development. I like FastCGI or SCGI with a dedicated webserver as a frontend for production.

(posted to blog as well) would like to know more about the strengths/weaknesses of these development resources. For example, one of the things i love about the django dev server is that it "listens" to all the project dependencies and restarts when any file is saved (which has saved me from trying to understand why something I fixed didn't work and discovering that it's because the changes weren't .pyc'd)

Flask/Werkzeug does that as well, provided your app is in debug mode.

For flask it's...

    app.run(debug=True)

Or having `DEBUG = True` somewhere in your config object/file.

One thing about that though, Flask seems to monitor file changes in its project tree and reload whenever any of the files have changed, and with my OCD symptom of saving after every few dosen keystrokes, the reload script keps crashing on syntax errors taking the rest of the server with it.

Same for CherryPy, more or less.

I'm not a big fan of auto-restart. It's slow for the server to crawl over all files and check if re-load is needed. Having individual modules reload themselves without reloading the whole server is error prone (e.g. you could end up using an old class).

With Quixote I have a Tkinter GUI that shows me the debug and access logs and lets me restart the DB or app server with a single click. When I'm ready to test I just right-click on that window and the app server restarts.

If this matters — and the reload feature is for development, so I'm not sure the polling has a noticeable impact — an inotify implementation is also possible.

That's not a bad overview, but what's the point? How one way is better than the other? Does it make any difference which development server to use?

As I mentioned in my first post (http://pyrseas.wordpress.com/2011/12/26/python-web-framework...), "I’ve been researching web frameworks, partly with a view to writing my own, and thought I’d share my findings." I'm not trying to judge these frameworks from the perspective of a developer (at least not completely), but rather from the POV of "if I were writing a framework, which features are essential, which nice to have, which I can disregard." This is in contrast to the the framework "battles," "shootouts" or "peformance matchups" elsewhere.

Although it's not stated, the point is that pretty much every framework that is not based on Twisted uses BaseHTTPServer which is known only to run in single-process mode, meaning that you should NEVER use it anywhere near production environment.

I am not sure what you mean by "single-process mode", but I am guessing that you are referring to the ability to serve more than one request at a time. If this is the issue, then BaseHTTPServer works just fine in production environments if a thread pool is used or if multiple instances of the application are run behind a reverse proxy.

Sorry I wasn't clear, I meant serving more than one request at a time, and apparently this is even possible without using multiple instances, use multiple inheritance with a threading mixin. This is not going to be properly concurent due to GIL limitations but it should be good enough -- http://blog.doughellmann.com/2007/12/pymotw-basehttpserver.h...

However this setup can lead to socket lockup (see picked answer) -- http://stackoverflow.com/questions/5693741/whats-difference-...

I am not sure what you mean by "properly concurrent", but I am guessing that you are referring to the fact that Python code cannot use more than one core because of the GIL. This limitation also applies to Twisted applications.

For high volume apps, it often makes sense to run multiple instances of the app behind a reverse proxy. That's the only way to make full use the CPU when running Python.

What is "socket lockup"? The word "lockup" is nowhere to be found on the page you references.

Sometimes I have problems with runserver and IE. I forgot exactly why (probably multiple requests) but fixed it by using this:

https://github.com/ashchristopher/django-concurrent-server

Really nice module.

The twisted.web server is nice because you can both develop on it and deploy it with minimal configuration. Using twisted.web.wsgi.WSGIResource, you can use it to serve normal WSGI sites, too. It's handy for running multiple sites on different ports.

It doesn't automatically reload on file changes, but PyQuitter[1] can provide that functionality, so it's not a huge issue.

1. https://github.com/ludios/Pyquitter

What this article taught me is the mind-boggling plethora of Python web frameworks out there. I'm heavily into Django myself, and it does well enough that I'm curious as to the demand for the other frameworks. How many Python web frameworks do you really need in 2012?

For me? Two.

Django is good for getting a site/system up and running fast, so long as I'm not too concerned with specific implementation details (the users 'just work', etc.)

Pyramid is good for a longer-term/more custom system where being easily able to modify (or choose) particular implementation details is important to me. It's not as fast to get a full-featured site off the ground, but the pieces glue together in a way that I really like.

I think that there was a well known post many years ago about "glue" and "full stack" frameworks, comparing pylons (now pyramid) as the former, and django as the latter.

#EDIT: Oh, and I used to do a bit of work with Zope/Plone, but that's pretty much what you'd consider to be the 'enterprisey' setup for python, and I wouldn't recommend it for most uses.

That mirrors exactly our experience. We have used Pyramid for three recent project and its awesome. It just takes a little longer, but its flexibility is impressive. We've just used it with Pure templates also, which I was very impressed with

There is always a demand for something that feels and acts less monolithic.

There can only be one! Pyramid

Reply on news.ycombinator.com