I'm curious to know whether ArcGIS Desktop 10.0 will support newer versions of Python than 2.6. And for that matter newer versions of NumPy (ie, 1.4, 1.5 etc). I'm sure that this documentation is on the ESRI site somewhere, but I can't find it.
I have found that ArcGIS Desktop 10.0 will respect an existing Python 2.6 install as long as you have Numpy 1.3.0 installed (ref), and I'm guessing, at least until Numpy 1.5.0 is out and supporting Python 3, then no Python 3 for ArcGIS, but I'd still be interested to know if upgrading is possible when it's available.
Best Answer
Nope, one version of Python per release of ArcGIS. The reason for this is simple: most of the magic happens in a C extension (arcgisscripting). The C APIs change from version to version, and that DLL isn't going to play nice in other versions of Python.
However, every time the main Python.org site releases a security fix (2.6.X), those are binary compatible and can be installed.