The newest samba4 alpha is not possible to compile with python2.4.3. I heard from some of the developers that its supposed to work with python2.4.3, aswell.
This information is far away from being enough. First, yes - it's true, python 2.4 should be supported. If you don't believe it look at this buildfarm (automated build) host: http://build.samba.org/?function=View+Build;host=ultra5;tree=samba_4_0_test;compiler=gcc
Therefore I think your problem might be related to a "broken" build. If you checked out from GIT run a "git clean -d -f -x ." in the repo root dir to clean up all generated files (binaries, headers...). If you use an archive remove the extracted content and simply redecompress it. Then do a full build from scratch.
If the problem persists please report: OS, platform, exact error message, release number of s4 ("alphaXX"), special constellations (e.g. more python environments installed?).
Only then we can try to find a solution.
I close this since it's very unlikely that Python is the real cause of your build problem. Maybe you have only some misconfiguration regarding it. If you need some help to configure it properly please write to "firstname.lastname@example.org" or talk in the #samba-technical IRC chat.