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update-alternatives for python3 on Ubuntu

Ubuntu 16 default python is almost python 3

Loads of solutions exist, but for changing the system default, alias is not the way to go.

$ update-alternatives --list python update-alternatives: error: no alternatives for python

ls -larth `which python`*
-rwxr-xr-x 2 root root 4.3M Nov 17 19:23 /usr/bin/python3.5
-rwxr-xr-x 1 root root 3.4M Nov 19 09:35 /usr/bin/python2.7
lrwxrwxrwx 1 root root   24 Feb  5 09:36 /usr/bin/python -> /etc/alternatives/python

So we have 2 - use these in update-alernatives

sudo update-alternatives --install /usr/bin/python python /usr/bin/python2.7 1
sudo update-alternatives --install /usr/bin/python python /usr/bin/python3.5 2

$ sudo update-alternatives --config python
There are 2 choices for the alternative python (providing /usr/bin/python).

  Selection    Path                Priority   Status
* 0            /usr/bin/python3.5   2         auto mode
  1            /usr/bin/python2.7   1         manual mode
  2            /usr/bin/python3.5   2         manual mode

Press <enter> to keep the current choice[*], or type selection number:


$ python --version
Python 3.5.2
$ python2 --version
Python 2.7.12
$ python3 --version
Python 3.5.2
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Updated gist with python3 at Credits added and thanks patrickmmartin!

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Can anyone comment as to whether this is problematic on Bionic? Ref:

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hemulin commented Oct 5, 2018

Just followed it after upgrading to 18.04.1. It worked great.

Thanks 👍

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javiergarval commented Feb 12, 2019

Changing between python configurations (python2 to python3.7) give me this thread error:

Original exception was:
Traceback (most recent call last):
  File "/usr/bin/pip", line 9, in <module>
    from pip import main
ImportError: cannot import name 'main' from 'pip'

Which is properly solved modifying /usr/bin/pip file with this:

from pip import main
if __name__ == '__main__':

But, again, if I change the python interpeter, pip conf is complaining.

Do you know any possible solution?


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That worked for me.....thanx

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MVoz commented Nov 13, 2019

sudo update-alternatives --install /usr/bin/python python /usr/bin/python2.7 1
sudo update-alternatives --install /usr/bin/python python /usr/bin/python2.4 5

sudo update-alternatives --install /usr/bin/python3 python3 /usr/bin/python3.5 5
sudo update-alternatives --install /usr/bin/python3 python3 /usr/bin/python3.7 1

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duwudi commented Jan 5, 2021


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50935 commented Feb 10, 2021

Hello , when i started upgrade python 3,

dpkg: error: unable to create new file '/var/lib/dpkg/arch-new': permission denied

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arky commented May 17, 2022

On Ubuntu 22.04 LTS. You'll need to add Deadsnakes ppa to ensure you have python 3 version (3.8, 3.9) available.

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