Well, broadly, the reason is that it allows version-specific code to be included in libraries.I recently installed python 2.4, and many installed software packages stopped working. Some things got working after I copied some files and directories from /usr/lib/python2.3/site-packages to /usr/lib/python2.4/site-packages, but I also had to install a newer PyXml package, as some of the files that came with python2.4 required a newer version of pyxml than I had in python2.3/site-packages.
I wonder if there is any particular reason I have no /usr/lib/site-python directory, and everything is installed in version-specific site-packages.
Of course, Python is so good at maintaining backward compatibility that it's unlikely a pure Python module will fail to run on the next version of Python. But you have to do this for extension modules, where the code is compiled against a specific version of the Python interpreter API, which doesn't stay the same from one version to the next.
The current "correct" philosophy is to have version-specific libraries. Of course, there is nothing to stop you building your own *no*-version-specific library directory and configuring it on to the PYTHONPATH for each version you run.I have Fedora Core 3. Is it the Fedora packagers who prefer installing everything in the version-specific directory? Is there no way to have older packages continue working in the presence of python2.4? (I still want the newest to be the default!)
I have tried (cd /usr/bin; grep '#!.*python' * 2>/dev/null), and very few of the programs have a specific version in the interpreter line. Is there any good reason this is so?
Thinking about it, a particular python program may require a particular module, but not any particular version of python or the module. The module perhaps requires at least python2.3, but could run just as well with python2.4 or later. It does not make sense to have the program demand a particular version of python in its interpreter string (e.g., "#!/usr/bin/python2.3"), but what about the module. Would it be better to put the module in site-python and include code to check the interpreter version?
Perhaps there is no perfect solution that covers all permutations, but on the other hand, what is currently the "correct philosophy" of version handling?
regards Steve -- Meet the Python developers and your c.l.py favorites March 23-25 Come to PyCon DC 2005 http://www.pycon.org/ Steve Holden http://www.holdenweb.com/ -- http://mail.python.org/mailman/listinfo/python-list
