I found it difficult to make Python 2.6 the default distribution for RHEL. It jacks up YUM when you do it. So I'm abandoning that approach altogether. The following notes were taken before I decided to take a different approach.
Python 2.4 is the python that ships with RedHat Enterprise Linux 5. This will never do.
I didn't remove 2.4 because some suggested against it, saying that RedHat needs to keep this version around.
Suppose you want to go to version 2.6. Here's what to do: either install from repo (yum install python26), which requires that you enable EPEL, or build from Python from source. It will install along side 2.4. When you next run Python you will find that the OS is still defaulting to 2.4. To fix this run update-alternatives.
update-alternatives --config python
Run Python again and your system wide default should now be the latest version you installed.
Alert: After building my own 2.6 and following the process above, I discovered that I had inadvertently screwed up YUM. Beware this process until I post final comments.