Edit (May 2019): Modified some of the code so that it would be compatible with Python 3.x

I’m a very minimal person when it comes to frameworks, I don’t generally like something that needs to generate an entire application file structure like you’d see with Django. When I was searching around for various frameworks to get me started with python and web development, I investigated the usual; DJango, CherryPy, Web.Py. I fell in love with circuits due it’s ease and simplicity, yet it can be quite powerful. This article will show you how to get Nginx setup with uWSGI along with a sample circuits.web application.

Nginx, as of version 0.8.40, comes deployed with the uwsgi module unless otherwise excluded (ie: –without-http_uwsgi_module), the older legacy version 0.7.63 and above came with the module, but needed to be compiled into it. The syntax I use in this article conforms to 0.8.40 and newer and might not work with an older version of Nginx. (Currently I’m using this on Nginx 1.10.3, with Python 2.7.13 & 3.5.3)

This article assumes you already have Nginx 0.8.40+ and Python installed.

Installing the uWSGI server

As stated on their wiki, “uWSGI is a fast (pure C), self-healing, developer/sysadmin-friendly application container server.”, it utilizes the uwsgi protocol (notice the all-lowercase spelling), and supports WSGI applications served from it.

Once you’ve downloaded the source from the wiki, you can install it (a number of methods here). For my purpose I’ve moved the compiled uwsgi binary to my /usr/local/bin folder so that I could call it from anywhere on my system.

The python module for uwsgi should be installed as well.

# pip install uwsgi

And for Python 3

# pip3 install uwsgi

Other than FreeBSD I have not seen uWSGI readily available in most distribution’s package systems.

You can test your installation by moving out of the source folder, and calling the binary:

# uwsgi --version
uWSGI 2.0.18

Simple Hello world app without daemonizing uWSGI

Now we’re going to setup a very simple WSGI hello world application, and host it behind uWSGI and use Nginx to serve it. We’re not going to daemonize the uWSGI as such you’ll see it’s output in your terminal as connections are made. Also in Nginx we’ll simply send everything to the backend application for this demonstration.

Configure Nginx

server {
	server_name myapp.example.com;
 
	location / { 
		uwsgi_pass 127.0.0.1:3031;
		#You can also use sockets such as : uwsgi_pass unix:/tmp/uwsgi.sock;
		include uwsgi_params;
	}
}

If Nginx is currently running, either restart it, or you can reload the configuration with “nginx -s reload”.

Create a WSGI application
In your application folder create a python file, for example myapp.py:

def application(environ, start_response):
    start_response("200 OK", [("Content-Type", "text/plain")])
    return ["Hello World!"]

For Python 3 a major change is that UWSGI requires responses in bytes instances and not strings. The fastest way is to type a string response as a byte, handy for constructed responses, otherwise you can encode it as UTF-8.

def application(environ, start_response):
    start_response("200 OK", [("Content-Type", "text/plain")])
    return [b"Hello World!"]
    # or ["Hello World!".encode('utf-8')]

Deploy with uWSGI
Now we’ll want to deploy a simple single-worker uWSGI instance to serve up your application from your application folder:

# uwsgi -s 127.0.0.1:3031 -w myapp
*** Starting uWSGI 0.9.6.7 (64bit) on [Mon Jan 31 00:10:36 2011] ***
compiled with version: 4.4.5
Python version: 2.6.6 (r266:84292, Dec 26 2010, 22:48:11)  [GCC 4.4.5]
uWSGI running as root, you can use --uid/--gid/--chroot options
 *** WARNING: you are running uWSGI as root !!! (use the --uid flag) *** 
 *** WARNING: you are running uWSGI without its master process manager ***
your memory page size is 4096 bytes
allocated 640 bytes (0 KB) for 1 request's buffer.
binding on TCP port: 3031
your server socket listen backlog is limited to 100 connections
initializing hooks...done.
...getting the applications list from the 'myapp' module...
uwsgi.applications dictionary is not defined, trying with the "applications" one...
applications dictionary is not defined, trying with the "application" callable.
application 0 () ready
setting default application to 0
spawned uWSGI worker 1 (and the only) (pid: 20317)

Newer versions of UWSGI and Python 3 may require some additional flags:

# uwsgi -s 127.0.0.1:3031 --plugin python3 -w /home/youruser/www/app.domain.com/myapp.py
    ...

If you attempt to connect to the site, and all goes well you’ll see Hello World on the screen as well as some log outputs on your terminal. To shut down the uWSGI server use Ctrl+C on that screen.

Now for some fun with Circuits.web

Circuits is a Lightweight Event driven Framework for the Python Programming Language, with a strong Component Architecture. It’s also my favorite framework for deploying very simple web applications (but can be used for far more complicated needs, for example SahrisWiki).

For this article I’ll show you a few ways circuits.web can really simplify handling requests and URI parsing.

First thing we’ll need to do is get the circuits module installed into Python.

If you do not already have Python SetupTools, install them:

apt-get install python-setuptools

And then simply install via easy_install:

easy_install circuits

You can get the egg (2.6 only) or the source of Circuits 1.3.1 from PyPi.Python.org.

For Python 3 you can use pip3 (or easy_install)

pip3 install circuits

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