Python import error when execute Mercurial

Question

My system is RedHat 5 Linux and has default python 2.4 installed. In order to execute Mercurial1.81, I tried to upgrade python from 2.4 to 2.6 and save it in different directory.

Here are the commands I have used:

find -xdev -samefile /usr/bin/python | xargs rm

I was trying to remove the hardlink used to link between python and python2.6. then I used commands as:

 ln -s /usr/bin/python2.4 /usr/bin/python
 ln -s /usr/bin/python2.6 /usr/local/bin/python
 export PATH=/usr/local/bin:$PATH
 Change first line of hg to #!/usr/bin/env python
 PATHONHOME=/usr/lib/python2.6
 PATHONPATH=/usr/lib/python2.6 

Then when I typed "whereis python", here are the results.

python: /usr/bin/python2.4 
/usr/bin/python 
/usr/lib/python2.4 
/usr/lib/python2.6 
/usr/local/bin/python 
/usr/include/python2.4 
/usr/include/python2.6 
/usr/share/man/man1/python.1.gz

Then when I typed "which python", it pointed to "usr/bin/python".When I typed "python -V", it showed "python 2.4.3". It seems pointing back to 2.4.3. Then when I used the command

python -c "import sys; print '\n' .join(sys.path)"

it showed

   /usr/lib64/python24.zip
    /usr/lib64/python2.4
    /usr/lib64/python2.4/plat-linux2
    /usr/lib64/python2.4/lib-tk
    /usr/lib64/python2.4/lib-dynload
    /usr/lib64/python2.4/site-packages
    /usr/lib64/python2.4/site-packages/Numeric
    /usr/lib64/python2.4/site-packages/gtk-2.0
    /usr/lib/python2.4/site-packages

I tried to find the paths of python 2.6 by typing "find / -name python2.6", it showed

/usr/include/python2.6
/usr/lib/python2.6
/usr/lib64/python2.6

Here are my questions :
(1) How can I change the replace the results from the on-liner above to python2.6 ?
(2) Why cannot I find a directory such as /usr/bin/python2.6 or /usr/local/bin/python2.6 ? Does it mean I installed my python2.6 wrong or accidentally remove the directory ?
Is anything wrong about the results I got from those commands I entered ?
(3) Any idea how to make the system execute python2.6 when I used "hg push" ?
(4)Should I install the python2.6 again at /usr/local/bin ?

Thank you very much,

Answer 1

I'd suggest changing /usr/bin/python back to the system's Python 2.4 to avoid destabilizing your system. Do this by symlinking to /usr/bin/python2.4 and then adding a /usr/local/bin/python symlink to /usr/bin/python2.6.

Then alter your path in your shell rc file (~/.bashrc for example) to find the local python first (export PATH=/usr/local/bin:$PATH if it is not already in that order), then editing /usr/bin/hg 's first line to #!/usr/bin/env python so that it runs that by default within your user session.

If python is still trying to load the wrong version of the python libraries for whatever reason (2.4 when you're running the 2.6 python binary), you can change the search path the python executable will use to locate its home with the PYTHONHOME environment variable.

It's probably best not to change this system-wide, however, as there may be a lot of python scripts rolled into the OS which may not be compatible with Python 2.6. Try adding it to your shell rc file.

If for whatever reason PYTHONHOME doesn't do it, you can edit the PYTHONPATH environment variable directly (in your rc file), to which you can add the python 2.6 library paths.

I suggest mirroring the output of python -c "import sys; print '\n'.join(sys.path)".

This one-liner should show the python 2.6 paths when running python 2.6, but if it still shows 2.4 paths, you'll want to replace the paths it shows with the correct paths for python 2.6 (which will likely be the same, only with "6" instead of "4")

Answer 2

Your mercurial installation is in /usr/lib64/python2.4/site-packages/mercurial. That particular installation would require Python 2.4. And the first line of /usr/bin/hg is probably:

#!/usr/bin/python

Assuming you're using a package from the official repositories, Mercurial would depend on the default Python to be exactly version 2.4. So, messing with /usr/bin/python is not really a good idea. If it really bothers you, you could easy_install one on your new Python 2.6.