Changing your default python version on OSX

$ man python
$ which python
/usr/bin/python
$ python -V
Python 2.7.1
#
# temporarily change version
#
$ export VERSIONER_PYTHON_VERSION=2.6
$ python -V
Python 2.6.6
$ unset VERSIONER_PYTHON_VERSION
$ python -V
Python 2.7.1
#
# persistently change version
#
$ defaults write com.apple.versioner.python Version 2.6
$ python -V
Python 2.6.6

http://stackoverflow.com/questions/6998545/how-can-i-make-python-2-6-my-default-in-mac-os-x-lion