The Mac dev community has outgrown Python 2.5 it seems but you might still need it if, say, you work on a Google App Engine project. I recently set up a fresh new Snow Leopard machine and really didn't want to eff it up with Macports. I like Macports but it leaks dynamic libraries here and there and this screwed me on my last machine. Instead I've had good luck with Homebrew (so far) but I couldn't find a Python 2.5 recipe anywhere. Snow Leopard ships with a version of Python 2.5 but I ran into some trouble with it as soon as I tried using virtualenv. Apple usually messes up Python in some way so I figured I'd just compile one. Since I couldn't find anything succinct while searching online here are my notes.
All the kind folks who use Macports have patched the hell out of Python 2.5 so I took a trial and error approach: apply patches, compile, make, make test. When things failed I'd go back and apply some more patches. You have to watch out though because Macports does this odd thing where they patch in __PREFIX__ then replace it later with the Macports root path. I ended up only needing a few patches (I think) so here's what to apply. Get the patches from svn:
mkdir ~/tmp/macports-py25 cd ~/tmp/macports-py25 svn co http://svn.macports.org/repository/macports/trunk/dports/lang/python25
Download Python 2.5.5, cd into the source, and apply these:
cd ~/src/Python-2.5.5 patch -p0 -r . < ~/tmp/macports-py25/python25/files/patch-configure-badcflags.diff patch -p0 -r . < ~/tmp/macports-py25/python25/files/patch-64bit.diff patch -p0 -r . < ~/tmp/macports-py25/python25/files/patch-Modules-posixmodule.c.diff patch -p0 -r . < ~/tmp/macports-py25/python25/files/patch-pyconfig.h.in.diff patch -p0 -r . < ~/tmp/macports-py25/python25/files/patch-FSIORefNum.diff
Compile and run the tests (they take a long time)
./configure --prefix=/usr/local/python2.5.5 \ --with-universal-archs="64-bit" \ MACOSX_DEPLOYMENT_TARGET=10.6 \ CFLAGS="-arch x86_64" LDFLAGS="-arch x86_64" make make test sudo make install
Now bask in anticlimactic glory that you still have to use Python 2.5 for something!