Snow Leopard’s Python 2.6 site-packages (and a psycopg2 issue)

THE ULTIMATE EDIT: I’ve got new instructions on how to conquer Symbol not found: \_PQbackendPID! Check them out here.

Maybe I’m a newb, maybe I’m not a newb. But I had a hard time installing Django (from scratch) on my new install of Mac OS X 10.6 Snow Leopard. It appears my issue was with the site-packages location. It’s got python26 installed by default, installed in

 /System/Library/Frameworks/Python.framework

So I ran my handy site-packages finding command:

 python -c "from distutils.sysconfig import get_python_lib; print get_python_lib()"

It gave me this path.

 /System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages

So I linked Django to that directory. But when I tested my setup to see if it would load the Django modules, it wouldn’t. So I printed my pythonpath (going into the python shell and running import sys; print sys.path) and I found the only default site-packages directory in pythonpath.

 /Library/Python/2.6/site-packages

Once I linked Django there, it worked like a charm. Hope this saves you a 5-minute headache or something.

Update: I also ran into a bit of a tiff installing psycopg2 from source. I ran the following commands, which installed psycopg2 into the previously-listed System site-packages path:

 python setup.py build
 sudo python setup.py install

Rather, once I ran the easy install command (the setuptools for this seem to be included), my python setup found all the modules it needed for PostgreSQL integration.

 easy_install .

Again, hope this helps another 5-minute headache!

Another edit: there’s been some discussion in the comments about a problem with PostgreSQL/Python integration throwing errors in Snow Leopard. Namely, it’s the following error message:

 Symbol not found: _PQbackendPID

The general, scientific Internet consensus is that it’s due to a weird mixture of 32-bit plugins with a 64-bit process. Until more and more things become available as 64-bit, you’ll probably want to run Apple’s build of Python 2.6 as 32-bit for the time being. Here’s the terminal command to do just that.

 defaults write com.apple.versioner.python Prefer-32-Bit -bool yes

Not sure if that needs to be run with sudo, but there you have it. Thanks to @Mark and @John Simons for laying this out and explaining it.