Change default Python version

rocka · 12-08-2007, 09:52 AM

I am running Debian Etch 4.0 and I am trying to change the default python version to 2.5. I used apt-get install python2.5 and the package installed successfully, but typing:
python -V
still gives me:
Python 2.4.4

Any help would be greatly appreciated.

Vookimedlo · 12-09-2007, 03:18 AM

Hi,

Have you tried update-alternatives? This should be a standard way how to switch default version of given program between multiple versions.

rocka · 12-09-2007, 05:18 AM

Quote:

Originally Posted by Vookimedlo

Hi,

Have you tried update-alternatives? This should be a standard way how to switch default version of given program between multiple versions.

I have tried: "update-alternatives --config python"
that gives me:
"No alternatives for python."

makuyl · 12-09-2007, 10:32 AM

How about changing the symlink, i.e:

Code:

ln -s /usr/bin/python2.4  /usr/bin/python

My setup:

Code:

:~$ls -l $(which python)
lrwxrwxrwx 1 root root 9 Jun  2  2007 /usr/bin/python -> python2.4
:~$ls -l /usr/bin/python*
lrwxrwxrwx 1 root root       9 Jun  2  2007 /usr/bin/python -> python2.4
lrwxrwxrwx 1 root root      16 Jun  2  2007 /usr/bin/python-config -> python2.4-config
-rwxr-xr-x 1 root root  946284 Oct 19  2006 /usr/bin/python2.3
-rwxr-xr-x 1 root root 1018188 Aug 16 03:05 /usr/bin/python2.4
-rwxr-xr-x 1 root root    1276 Aug 16 03:04 /usr/bin/python2.4-config
-rwxr-xr-x 1 root root 1149812 Aug 17 01:52 /usr/bin/python2.5

rocka · 12-09-2007, 01:09 PM

Thank you for your reply. Tried it, didn't help:

Code:

ln -s /usr/bin/python2.4  /usr/bin/python
ln: creating symbolic link `/usr/bin/python' to `/usr/bin/python2.4': File exists
:~# ln -s /usr/bin/python2.4  /usr/bin/python2.5
ln: creating symbolic link `/usr/bin/python2.5' to `/usr/bin/python2.4': File exists

Code:

:~# ls -l $(which python)
lrwxrwxrwx 1 root root 9 2006-07-22 13:49 /usr/bin/python -> python2.4
~# ls -l /usr/bin/python*
lrwxrwxrwx 1 root root       9 2006-07-22 13:49 /usr/bin/python -> python2.4
-rwxr-xr-x 1 root root 1015360 2007-04-05 20:12 /usr/bin/python2.4
-rwxr-xr-x 1 root root 1139848 2006-12-09 14:37 /usr/bin/python2.5

Code:

:~# python -V
Python 2.4.4

Did I do something wrong? Any other suggestions. I also tried to remove python 2.4 and re-install python 2.5. Still after this it's listing python 2.4.4 as the active.

makuyl · 12-09-2007, 03:31 PM

Well, if the link exists, remove it: "rm /usr/bin/python". Then make the link with ln -s
In my example output the files with a "->" pointing to a real file, are links. The links you can remove to change them.
You have python pointing to python2.4 . If you want 2.5 do:
rm /usr/bin/python
ln -s /usr/bin/python2.5 /usr/bin/python

rocka · 12-09-2007, 05:05 PM

That sure did work. Thank you very much makuyl

makuyl · 12-10-2007, 12:30 PM

You're welcome.
PS: you can't link a binary (executable) to another binary. Symbolic links are like windows (or any os's) shortcuts, so this:

Quote:

Originally Posted by rocka

Code:

:~# ln -s /usr/bin/python2.4  /usr/bin/python2.5
ln: creating symbolic link `/usr/bin/python2.5' to `/usr/bin/python2.4': File exists

won't work as both those files are binaries. You create a link to a binary as you did, or you can create several link layers as in link->link->binary.

Code:

man ls

type "q" to quit.

jameslaw · 04-11-2008, 04:34 PM

Changing the link may work, but I'm not satisifed this if the "official" way to change the default python version. If I look in my /usr/bin, I have python2.4 and python2.5 installed and 2.4 is the default.

lrwxrwxrwx 1 root root 9 2007-06-13 18:32 /usr/bin/python -> python2.4
-rwxr-xr-x 1 root root 1021516 2008-03-11 17:17 /usr/bin/python2.4
-rwxr-xr-x 1 root root 1173364 2008-03-08 20:42 /usr/bin/python2.5

However, in that same dir there is also:

lrwxrwxrwx 1 root root 29 2007-06-13 18:32 /usr/bin/pyversions -> ../share/python/pyversions.py

If I look in /usr/share/python, I have:

-rw-r--r-- 1 root root 288 2007-05-03 21:28 debian_defaults
-rwxr-xr-x 1 root root 12158 2007-05-16 23:19 pyversions.py

And, the contents of debian_defaults is:
---begin---
[DEFAULT]
# the default python version
default-version = python2.4

# all supported python versions
supported-versions = python2.4, python2.5

# formerly supported python versions
old-versions = python2.3

# unsupported versions, including older versions
unsupported-versions = python2.3
---end---

So, how do I change the default version so that I know the debian management system knows what is going on?

arctan1701 · 03-31-2009, 03:37 AM

Quote:

Originally Posted by jameslaw

Changing the link may work, but I'm not satisifed this if the "official" way to change the default python version. If I look in my /usr/bin, I have python2.4 and python2.5 installed and 2.4 is the default.

[snip]

So, how do I change the default version so that I know the debian management system knows what is going on?

this is what you are looking for:

http://codeghar.wordpress.com/2009/0...ves-in-debian/

Telemachos · 03-31-2009, 08:38 AM

Quote:

Originally Posted by arctan1701

this is what you are looking for:

http://codeghar.wordpress.com/2009/0...ves-in-debian/

That blog post recommends using sudo. On a default Debian setup, sudo is not enabled. (The blog author may be coming from an Ubuntu background, or they may like this kind of setup.) So, for anyone who tries this: substitute su.

More generally, I would not recommend changing the links in /usr/bin by hand, and there are other ways to skin this cat. If you really wanted a specific version of Python to be found as the default (ie, simply by typing python), I would prefer this: (1) make a symlink to $HOME/bin/python and then (2) make sure that $HOME is earlier in my $PATH than /usr/bin. This is cleaner, I think, and it avoids messing with the system defaults.

vlademir · 03-31-2009, 09:01 AM

Hi,

Please see this link surely will help you
http://forums.freebsd.org/showthread.php?t=1390

makuyl · 03-31-2009, 01:26 PM

If you don't want to mess with the symlinks, you can use the debian way update-alternatives without sudo

Code:

:~# update-alternatives --install /usr/bin/python python /usr/bin/python2.4 10
:~# update-alternatives --install /usr/bin/python python /usr/bin/python2.5 20

As a side note, why are you necro posting?

Telemachos · 03-31-2009, 05:26 PM

Quote:

Originally Posted by makuyl

As a side note, why are you necro posting?

Damn. I can't speak for Arctan1701, but I necro-posted (!) because this thread ended up on the top of the Debian forum (after Arctan bumped it) and the sudo advice bugged me. I have to start checking dates more carefully.