documentation suggestion
It would be helpful if the documentation made explicit exactly what "pythonbrew switch ..." does. Presumably it modifies the path so only the selected python and its installed-scripts are in the path. Does it also change the PythonPath? How about the current framework version on MacOS X (e.g. /System/Library/Frameworks/Python.framework/Versions/Current or /Library/Frameworks/Python.framework/Versions/Current)?
Thank you for clarifying.
The pythonbrew code is pretty easily understandable, so you just need to check the source code for the switch command.
Using pythonbrew switch will add ~/.pythonbrew/bin, ~/.pythonbrew/pythons/Python-3.2.3/bin to your $PATH, as well as override your $PYTHONPATH with ~/.pythonbrew/pythons/Python-3.2.3/lib. Replace 3.2.3 with whichever Python version you switched to.