Winning at the shell game: iPython on Google App Engine

iPython is an awesome extended Python shell that gives you goodies like tab completion for instances, history tracing (so you can easily copy interactive sessions as doctests), etc. And, if you install it, your Django project on Google App Engine will automatically start using it instead of the regular python shell when you use ./manage.py shell.

To install iPython on OS X Tiger (yes, my Leopard discs are still safely in their box since I downgraded and I don't see any reason to bring them back out yet), I followed the following steps:

  1. Download the latest iPython from the iPython distributions page (ipython-0.8.4.tar.gz)
  2. Untar it, cd into the folder
  3. As per the instructions on the iPython download page: 

    python setup.py build
sudo python setup.py install
  4. To test it out on my Google App Engine/Django project, from my project folder: ./manage.py shell

(Note: The docs mention that you need to have readline installed on Mac OS X in order to use some of the features like tab completion and syntax highlighting. It just worked out of the box for me on OS X Tiger 10.4.11 -- I'm not sure if I had installed readline at some point or whether it was just there. Check out these instructions if you're having trouble.)

Once you have it installed, try out the cool code completion: 

from my_app import models
models.

Press ⇥, and you'll see a list of all your models. models.my_model. ⇥ will show you the properties for that model and so on.

To create doctests, simply enter your test instructions in the shell and then type hist -n to get a dump of your history without line numbers that you can copy and paste into your doctest.

You can press ⌃ P and ⌃ ⇧ P to interactively bring up the previous and next commands in the history. If you've typed a bit of the command before doing this, it will filter to show you only those commands from your history that match the text you've entered.

You can also access the system shell without leaving iPython by preceding system calls with an exclamation mark. !ls, for example, will show you a listing of the current working directory.

And there's much more you can do that you can read about on the iPython documentation (or just type ? in the iPython shell itself and browse the docs interactively).

Check out iPython, it's yummy!

I found out about iPython from an excellent blog post by AkH on useful tips and good practices for Django projects. Thanks, dude!

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