In this Linux tutorial, you will learn how to use Alternatives command to set Python Versions in Linux. #centlinux #linux #python
Table of Contents
Problem Statement:
We have two versions of Python Programming Language are already installed on our Rocky Linux 9 server.
Python 3.9 is by default installed on all Red Hat Enterprise Linux 9 operating systems including Minimal installations.
Install Python on Linux:
We have installed Python 3.10 on this machine, and can also install the same by following our previous article: How to install Python 3.10 on Rocky Linux 9
Verify the existance of Python versions by executing following commands.
# python3.9 -V Python 3.9.14 # python3.10 -V Python 3.10.4
Alternatives Command Usage:
Linux operating system provides alternatives command to set an active link to a specific command, among all the installed versions of that command.
Use the following command to set an active version of Python.
# alternatives --config python
If the above command returns no output, check whether python is available in commands list known to alternatives.
# alternatives --list libnssckbi.so.x86_64 auto /usr/lib64/pkcs11/p11-kit-trust.so soelim auto /usr/bin/soelim.groff iptables auto /usr/sbin/iptables-nft ebtables auto /usr/sbin/ebtables-nft arptables auto /usr/sbin/arptables-nft cifs-idmap-plugin auto /usr/lib64/cifs-utils/cifs_idmap_sss.so man auto /usr/bin/man.man-db ld auto /usr/bin/ld.bfd
You can see that, there is no python command in list. Therefore, you have to add Python in alternatives info base.
Check the location of Python executable files.
# whereis python3.9 python3.9: /usr/bin/python3.9 /usr/lib/python3.9 /usr/lib64/python3.9 /usr/include/python3.9 /usr/share/man/man1/python3.9.1.gz # whereis python3.10 python3.10: /usr/local/bin/python3.10 /usr/local/lib/python3.10
Note down the location of Python executables from above output and then execute following commands to define Python alternatives.
# alternatives --install /usr/bin/python python /usr/bin/python3.9 1 # alternatives --install /usr/bin/python python /usr/local/bin/python3.10 2
You can now execute following command to set an active version of Python command.
# alternatives --config python There are 2 programs which provide 'python'. Selection Command ----------------------------------------------- 1 /usr/bin/python3.9 *+ 2 /usr/local/bin/python3.10 Enter to keep the current selection[+], or type selection number:
Currently, Python3.10 is set as active Python command.
You can verify it by executing following command at Linux bash prompt.
# python -V Python 3.10.4
Now, change the active version of Python command to 3.9 as follows.
# alternatives --config python There are 2 programs which provide 'python'. Selection Command ----------------------------------------------- 1 /usr/bin/python3.9 *+ 2 /usr/local/bin/python3.10 Enter to keep the current selection[+], or type selection number: 1
Check the version of Python command again.
# python -V Python 3.9.14
Video of Alternatives Command Example:
Conclusion:
In this Linux tutorial, you will learn how to use Alternatives command to set Python Versions in Linux.