Archive for October, 2009

Tornado with VirtualEnv and Pip Quickstart

Friday, October 9th, 2009

Friendfeed’s open source Tornado web server is great, and is incredibly easy to get up-and-running. Just install tornado, write your app and run it.

At some point, however, you’d want more structure in your project and manage dependencies to ease deployment. This is where virtualenv and pip shines. For a few more steps, you can bootstrap your project and have the warm fuzzy feeling that you can easily deploy the stuff when the code is ready.

Installing virtualenv and pip

If you haven’t set up virtualenv, do so (as root):

# easy_install virtualenv

Decide where you’d put your project directory. I’ll use /path/to/myapp for now. The next step is to create a virtualenv where all your Python packages are stored. I like to use the convention of a directory called root where all dependencies are installed. I’d generally also use it as the prefix for any cmmi packages that I’d like to contain within the project.

$ cd /path/to/myapp
$ virtualenv --no-site-packages root

Activate the environment that we just created:

$ . root/bin/activate
(root)[wil@wasabi /path/to/myapp]$ 

From now on, all packages installed with easy_install will be placed in this virtualenv.

Next, we will install pip into this virtualenv:

(root)[wil@wasabi /path/to/myapp]$ easy_install pip

Once pip is installed, as long as you’ve got your virtualenv activated, anything installed with pip will also go into the right place (without your having to remember to use the -E command line argument.)

Installing Tornado

Tornado (as of the current version) needs two mandatory dependencies, i.e. pycURL and simplejson. Make sure you have the right libcURL version installed on your system (using apt-get or other mechanism) and pick the compatible pyCURL version.

(root)[wil@wasabi /path/to/myapp]$ pip install pycurl==7.16.4
(root)[wil@wasabi /path/to/myapp]$ pip install simplejson

Now we’ll install tornado proper. I chose to go with the bleeding edge and ask pip to install from the git trunk.

(root)[wil@wasabi /path/to/myapp]$ pip install -e \
  git+git://github.com/facebook/tornado.git#egg=tornado

Should you not want that, you can tell pip to install from the tarball URL instead (at least until tornado gets added to PyPI.)

(root)[wil@wasabi /path/to/myapp]$ pip install \

http://www.tornadoweb.org/static/tornado-0.2.tar.gz

Tornado is installed!

Every now and then, it’s a good idea to save your pip dependencies by running

(root)[wil@wasabi /path/to/myapp]$ pip freeze > pip-req.txt

Start your project

What I like about this is that the project directory has all the dependencies contained within a single directory (root). This is really just my convention; I’d create a src directory where my application code lives.

(root)[wil@wasabi /path/to/myapp]$ mkdir src
(root)[wil@wasabi /path/to/myapp]$ cd src
(root)[wil@wasabi /path/to/myapp/src]$ 

Let’s test drive Tornado:

(root)[wil@wasabi /path/to/myapp/src]$ cp ../root/src/tornado/demos/helloworld/helloworld.py .
(root)[wil@wasabi /path/to/myapp/src]$ python helloworld.py

From browser, visit your host at port 8888 to verify.

That’s it!