I have been looking at setting up a web server to use Python and I have installed Apache 2.2.22 on Debian 7 Wheezy with mod_wsgi. I have gotten the initial page up and going and the Apache will display the contents of the wsgi file that I have in my directory.
However, I have been researching on how to deploy a Python application and I have to admin, I find some of it a little confusing. I am coming from a background in PHP where it is literally install what you need and you are up and running and PHP is processing the way it should be.
Is this the same with Python? I can't seem to get anything to process outside of the wsgi file that I have setup. I can't import anything from other files without the server throwing a "500" error. I have looked on Google and Bing to try to find an answer to this, but I can't seem to find anything, or don't know that what I have been looking at is the answer.
I really appreciate any help that you guys can offer.
Thanks in advance! (If I need to post any coding, I can do that, I just don't know what you guys would need, if anything, as far as coding examples for this...)
Python is different from PHP in that PHP executes your entire program separately for each hit to your website, whereas Python runs "worker processes" that stay resident in memory.
You need some sort of web framework to do this work for you (you could write your own, but using someone else's framework makes it much easier). Flask is an example of a light one; Django is an example of a very heavy one. Pick one and follow that framework's instructions, or look for tutorials for that framework. Since the frameworks differ, most practical documentation on handling web services with Python are focused around a framework instead of just around the language itself.
Nearly any python web framework will have a development server that you can run locally, so you don't need to worry about deploying yet. When you are ready to deploy, Apache will work, although it's usually easier and better to use Gunicorn or another python-specific webserver, and then if you need more webserver functionality, set up nginx or Apache as a reverse proxy. Apache is a very heavy application to use for nothing but wsgi functionality. You also have the option of deploying to a PaaS service like Heroku (free for development work, costs money for production applications) which will handle a lot of sysadmin work for you.
As an aside, if you're not using virtualenv to set up your Python environment, you should look into it. It will make it much easier to keep track of what you have installed, to install new packages, and to isolate an environment so you can work on multiple projects on the same computer.
Related
I have a couple of Python 2.7 scripts I need to have them run from a webpage. I've never done this before, although I'm comfortable coding in Python and well versed in Linux, Apache, Nginx.
I see many different frameworks like the old CGI, WSGI, Django, etc.
I need some recommendations for a framework that would require not much changes on my Python code for it to run on a webpage.
It seems CGI would be fairly easy for me, but since there are many newer frameworks, I need some advices.
Thanks!
Flask is probably the most straightforward Python web framework to use. It touts itself as a micro framework, and is very, very fast to get up and running with.
If you have a relatively straightforward set of requirements, I'd highly recommend giving it a look over. You can find the "hello" world example on the project's homepage here: http://flask.pocoo.org/
Depending on your project's requirements (does it need to be highly available/resilient?), you may even be able to get by using Flask's built-in development webserver along with a process control system such as supervisord. I wouldn't recommend this for heavy or production workloads, but for something running out of production this set up would work just fine for you.
If you're looking for client side browser frameworks in Python, there are skulpt and brython.
When I was looking for a similar framework, I decided to learn leave python for a javascript framework (particularly AngularJS and Node JS) for a client side language. I personally felt that the size of community and learning resources available in those two areas were more robust, and provided greater opportunity to master the framework.
I've already looked at other threads on this, but most don't go into enough setup detail which is where I need help.
I have an Ubuntu based VPS running with nginx, serving PHP sites through php-cgi on port 9000.
I'd like to start doing more with Python, so I've written a deployment script which I essentially want to use as a post-receive hook on my local GitLab server as my first python script. I can run this script successfully by running python script.py on the command line but in order to use this as a post-receive hook I need it be able to access it via http.
I looked at this guide on the nginx wiki but partway down is says to:
And start the django fastcgi process:
python ./manage.py runfcgi host=127.0.0.1 port=8080
Now, like I said I am pretty new to python, and I have never used the Django framework. Can anyone assit on how I am supposed to start the fastcgi server? Do I replace ./manage.py with the name of my script? Any help would be appriciated as everything I've found online refers to working with Django.
Do I replace ./manage.py with the name of my script?
No. It's highly unlikely your script is a FastCGI server, or that it can accept HTTP requests of any kind since you mention running it over the command line. (From what little I know of FastCGI, an app supporting it has to be able to handle a stream of requests coming in over stdin in a specific format, so there's definitely some plumbing involved.)
I'd say the easiest approach would be to use some web framework just to act as HTTP/FastCGI middleware. For your use a "microframework" like Flask (or even Paste but I found the documentation inscrutable) sounds like it'd work fine. The idea would be to have two interfaces to your main code, one that can handle command line arguments, and one that can handle a HTTP request, ultimately both would just call one function that actually does the work. (If you want to keep the command-line version of the app.)
The Flask documentation also mentions using uWSGI or standalone workers as deployment options. I'm not familiar with the former; the latter I wouldn't recommend for a simple, low-traffic app for the same reasons as the approach in the next paragraph.
Considering you use a VPS, you might even be able to just run the app as a standalone server process using the http.server module, but I'm not sure that's the better choice unless you absolutely want to avoid using any sort of framework. You'd have to make sure the app starts up if the server is rebooted or that it restarts when it crashes and it seems easier to just have nginx do the job of the supervisor.
UPDATE: Scratch that, it seems that nginx won't handle supervising a FastCGI worker process for you, which would've been the main advantage of the approach. In light of that it doesn't matter which of the three approaches you use since you'll have to set up a service supervisor one way or the other. I'd say go with uWSGI since flup (which is needed for Flask+FastCGI) seems abandoned since 2011, and the uWSGI protocol is apparently supported in nginx natively. Otherwise you'd need to use a different webserver than nginx, one that will manage a FastCGI worker for you. If this is an option, I'd consider Cherokee, which can be configured using a web GUI.
tl;dr: you need to write a (very simple) webapp. While it is feasible to do this without a web framework of any kind, in my opinion using one is easier, since you some (nontrivial) plumbing for free and there's a lot of guidance available on how to deploy them.
I am wondering how to go about implementing a web application with Python.
For example, the html pages would link to python code that would give it increased functionality and allow it to write to a database.
Kind of like how Reddit does it.
If you're looking for server side programming with databases and html templates etc, I think Django is great, along with Pyramid. However, I use Flask ( http://flask.pocoo.org/ ) for this since it is easy to use, learn and deploy even though it may not have as much support as the before mentioned 2 framework since it's just a microframework, using the Jinja2 templating engine, including a development test server with it's own debugger.
On the other hand, if you're going for client-side programming (i.e. in browser implementation ) You can look up .NET Ironpython or even Brython which uses python like javascript.
You might want to check out mod_wsgi or mod_python.
What Is mod_wsgi?
The aim of mod_wsgi is to implement a simple to use
Apache module which can host any Python application which supports the
Python WSGI interface. The module would be suitable for use in hosting
high performance production web sites, as well as your average self
managed personal sites running on web hosting services.
-
Current State of Mod_Python
Currently mod_python is not under active development. This does not
mean that it is "dead" as some people have claimed. It smiply means
that the code and the project are mature enough when very little is
required to maintain it.
This is a good article from the Python website:
http://docs.python.org/howto/webservers.html
Plain CGI is a good starting point to learn about server side scripting, but it is an outdated technology and gets difficult to maintain after certain level of complexity. I would think it is no longer used in industrial-grade web server anymore. Plus you have to setup a web server and then install some module to interpret python script (like Apache with mod_python) just to get started.
I had some experience with Django (https://www.djangoproject.com/) and found it fairly easy to get started with since they come with development test server. All you need to have is a Python interpreter + Django and you can get up-and-running quickly and worry about the deployment setup later. They have pretty good documentation for beginner as well.
We have never used Python for a web site without a framework. In our case that is Django. In other words, we do not use Python for our web sites the way Perl can be used, just having Apache run a Perl script.
The recommendations you have received about Django are sound. If you go the Django route, Graham Dumpleton and the modwsgi Google group were very helpful to me. I could
not have gotten mod_wsgi deployed on Red Hat Enterprise 5 64-bit without Graham's help.
Whether you choose Django or "straight" Python, you will need to become familiar with mod_wsgi.
Good luck in quantum time, which means by now, I hope this all worked out for you.
Is it possible to eliminate the desktop and fully code and deploy a python/django application to the cloud from within a browser? I think Heroku makes it possible to do that with Ruby on Rails but I have not come across a Python/Django equivalent.
I think there are huge advantages of developing code in the cloud. No deployment overhead, no code versioning headaches (because the cloud will track all changes anyway), access your code from anywhere, even an iPad, if you want to make a small change to your production code. I think Heroku has already proven that this is the future of web development and browser based IDEs like Mozilla Bespin are already getting some traction.
I'm not really sure that Heroku does that, it just a cloud space for Rails.....like phpfog (php), dotcloud (many), appengine (java, python)....
I think http://kodingen.com/ is something more like what you ask, code in the web and deploy on it.....
Haven't tried Kodingen though....
As an updated answer to #jjchiw, Koding provides a you with Python2 and Python3, and gives you root access to a full Ubuntu VM, so everything will work just like you expect :)
I say updated, because Kodingen turned into Koding a year ago, and is under very active development.
Let me know if you have any questions :)
Good morning.
As the title indicates, I've got some questions about using python for web development.
What is the best setup for a development environment, more specifically, what webserver to use, how to bind python with it. Preferably, I'd like it to be implementable in both, *nix and win environment.
My major concern when I last tried apache + mod_python + CherryPy was having to reload webserver to see the changes. Is it considered normal? For some reason cherrypy's autoreload didn't work at all.
What is the best setup to deploy a working Python app to production and why? I'm now using lighttpd for my PHP web apps, but how would it do for python compared to nginx for example?
Is it worth diving straight with a framework or to roll something simple of my own? I see that Django has got quite a lot of fans, but I'm thinking it would be overkill for my needs, so I've started looking into CherryPy.
How exactly are Python apps served if I have to reload httpd to see the changes? Something like a permanent process spawning child processes, with all the major file includes happening on server start and then just lazy loading needed resources?
Python supports multithreading, do I need to look into using that for a benefit when developing web apps? What would be that benefit and in what situations?
Big thanks!
What is the best setup for a development environment?
Doesn't much matter. We use Django, which runs in Windows and Unix nicely. For production, we use Apache in Red Hat.
Is having to reload webserver to see the changes considered normal?
Yes. Not clear why you'd want anything different. Web application software shouldn't be dynamic. Content yes. Software no.
In Django, we develop without using a web server of any kind on our desktop. The Django "runserver" command reloads the application under most circumstances. For development, this works great. The times when it won't reload are when we've damaged things so badly that the app doesn't properly.
What is the best setup to deploy a working Python app to production and why?
"Best" is undefined in this context. Therefore, please provide some qualification for "nest" (e.g., "fastest", "cheapest", "bluest")
Is it worth diving straight with a framework or to roll something simple of my own?
Don't waste time rolling your own. We use Django because of the built-in admin page that we don't have to write or maintain. Saves mountains of work.
How exactly are Python apps served if I have to reload httpd to see the changes?
Two methods:
Daemon - mod_wsgi or mod_fastcgi have a Python daemon process to which they connect. Change your software. Restart the daemon.
Embedded - mod_wsgi or mod_python have an embedded mode in which the Python interpreter is inside the mod, inside Apache. You have to restart httpd to restart that embedded interpreter.
Do I need to look into using multi-threaded?
Yes and no. Yes you do need to be aware of this. No, you don't need to do very much. Apache and mod_wsgi and Django should handle this for you.
So here are my thoughts about it:
I am using Python Paste for developing my app and eventually also running it (or any other python web server). I am usually not using mod_python or mod_wsgi as it makes development setup more complex.
I am using zc.buildout for managing my development environment and all dependencies together with virtualenv. This gives me an isolated sandbox which does not interfere with any Python modules installed system wide.
For deployment I am also using buildout/virtualenv, eventually with a different buildout.cfg. I am also using Paste Deploy and it's configuration mechanism where I have different config files for development and deployment.
As I am usually running paste/cherrypy etc. standalone I am using Apache, NGINX or maybe just a Varnish alone in front of it. It depends on what configuration options you need. E.g. if no virtual hosting, rewrite rules etc. are needed, then I don't need a full featured web server in front. When using a web server I usually use ProxyPass or some more complex rewriting using mod_rewrite.
The Python web framework I use at the moment is repoze.bfg right now btw.
As for your questions about reloading I know about these problems when running it with e.g. mod_python but when using a standalone "paster serve ... -reload" etc. it so far works really well. repoze.bfg additionally has some setting for automatically reloading templates when they change. If the framework you use has that should be documented.
As for multithreading that's usually used then inside the python web server. As CherryPy supports this I guess you don't have to worry about that, it should be used automatically. You should just eventually make some benchmarks to find out under what number of threads your application performs the best.
Hope that helps.
+1 to MrTopf's answer, but I'll add some additional opinions.
Webserver
Apache is the webserver that will give you the most configurability. Avoid mod_python because it is basically unsupported. On the other hand, mod_wsgi is very well supported and gives you better stability (in other words, easier to configure for cpu/memory usage to be stable as opposed to spikey and unpredictable).
Another huge benefit, you can configure mod_wsgi to reload your application if the wsgi application script is touched, no need to restart Apache. For development/testing servers you can even configure mod_wsgi to reload when any file in your application is changed. This is so helpful I even run Apache+mod_wsgi on my laptop during development.
Nginx and lighttpd are commonly used for webservers, either by serving Python apps directly through a fastCGI interface (don't bother with any WSGI interfaces on these servers yet) or by using them as a front end in front of Apache. Calls into the app get passed through (by proxy) to Apache+mod_wsgi and then nginx/lighttpd serve the static content directly.
Nginx has the added advantage of being able to serve content directly from memcached if you want to get that sophisticated. I've heard disparaging comments about lighttpd and it does seem to have some development problems, but there are certainly some big companies using it successfully.
Python stack
At the lowest level you can program to WSGI directly for the best performance. There are lots of helpful WSGI modules out there to help you in areas you don't want to develop yourself. At this level you'll probably want to pick third-party WSGI components to do things like URL resolving and HTTP request/response handling. A great request/response component is WebOb.
If you look at Pylons you can see their idea of "best-of-breed" WSGI components and a framework that makes it easier than Django to choose your own components like templating engine.
Django might be overkill but I don't think that's a really good argument against. Django makes the easy stuff easier. When you start to get into very complicated applications is where you really need to look at moving to lower level frameworks.
Look at Google App Engine. From their website:
Google App Engine lets you run your
web applications on Google's
infrastructure. App Engine
applications are easy to build, easy
to maintain, and easy to scale as your
traffic and data storage needs grow.
With App Engine, there are no servers
to maintain: You just upload your
application, and it's ready to serve
your users.
You can serve your app using a free
domain name on the appspot.com domain,
or use Google Apps to serve it from
your own domain. You can share your
application with the world, or limit
access to members of your
organization.
App Engine costs nothing to get
started. Sign up for a free account,
and you can develop and publish your
application for the world to see, at
no charge and with no obligation. A
free account can use up to 500MB of
persistent storage and enough CPU and
bandwidth for about 5 million page
views a month.
Best part of all: It includes Python support, including Django. Go to http://code.google.com/appengine/docs/whatisgoogleappengine.html
When you use mod_python on a threaded Apache server (the default on Windows), CherryPy runs in the same process as Apache. In that case, you almost certainly don't want CP to restart the process.
Solution: use mod_rewrite or mod_proxy so that CherryPy runs in its own process. Then you can autoreload to your heart's content. :)