The comprehensive uninstallation directions for MacPython comprise the single sentence: "To uninstall MacPython, you can simply remove these three things." The three things refer to the MacPython 2.5 application folder (/Applications/MacPython), the framework (/Library/Frameworks/Python.framework), and (I'm assuming) the symlink in /usr/local/bin.

Unfortunately, what it doesn't tell you is that unless you also remove all files with names starting with Python under /Library/Receipts, the installer won't let you reinstall MacPython (it checks these to see what is already installed). Instead the installer tells you that a newer version is installed, marks the files "skip", and fails with "nothing to install".

I spent a good few hours until I realized this so I hope this helps someone else keep their hair.

The MacPython re-install gotcha article by Aral Balkan, unless otherwise expressly stated, is licensed under a Creative Commons Attribution-Noncommercial 2.0 UK: England License.