Python seems broken on 16.04 LTS

[monkeybrain20122]

With 18.04, you get python3.
https://wiki.ubuntu.com/BionicBeaver/ReleaseNotes

That is strange

$ lsb_release -a
No LSB modules are available.
Distributor ID:    Ubuntu
Description:    Ubuntu 18.04.2 LTS
Release:    18.04
Codename:    bionic
$ which python
/usr/bin/python
$ python --version
Python 2.7.15rc1

[rsteinmetz70112]

Oops too late. Looks like already you have removed python2 and all the "autoremoves" hence broken your system. At this point may be a reinstallation is the least painful way. And why do you login as root?? Again this may be another reason that caused your issue in the first place.

I haven't removed it, since there were so many dependencies.
When I

# apt autoremove

I don't seen any packages to be removed.
When I

apt -remove python2.7

I see what I posted.
That's odd.
Typically when doing serious administration or trouble shooting I sudo -i to keep from typing sudo over and over again. I exit as soon as I'm finished.
I've been administering Unix systems for a long time so I'm comfortable as root.

[rsteinmetz70112]

Well you haven't explained what your problem is, and why do you have so many versions of python2 and 3???

I tried to run

# do-release-upgrade

and the script failed to run see my other thread

DO NOT try to remove python-2.7 since it is a dependency for many system components and if you remove it your system will break beyond repair.

I haven't

FYI 18.04 still uses python-2.7 as default so "upgrading" will not give you python3 as default, but it doesn't really matter though, as long as Ubuntu's team maintains it, the system's default python is just for maintenance, running and installing things.

That's why I need to fix this. The other versions of python were likely installed as dependencies of other packages. I didn't install them. IN fact the first part of the upgrade runs a script named bionic

#!/usr/bin/python3

from DistUpgrade.DistUpgradeMain import main
import sys


if __name__ == "__main__":
    sys.exit(main())

that refers to python3 which is linked to python3.5

# ls -ld /usr/bin/python3
lrwxrwxrwx 1 root root 9 Mar 23  2016 /usr/bin/python3 -> python3.5

On the other hand you can use different versions of python in your work without tempering with the system's . But update-alternatives is NOT the way to do it because many system components are compiled based on the version that comes with the system, and by changing the default via update alternatives again you break your system (that is probably what caused your issue in the first place)

The default has not been changed on purpose.

There are many ways to use different versions of python safely, e.g anaconda or virtualenv. I compiled python3.7 in my $HOME from source and invoke it with a script that sets all the environmental variables (Ubuntu 16.04), --I prefer it to Anaconda because the latter installs other stuffs I don't need, but Anaconda is a lot easier to setup if you are not very experienced, --but I don't remove the system's python3.5, nor do I try to override it with update-alternatives.

I haven't done any of that.

[oldfred]

Python will be python2 as link. Not sure if they can change that as then it would break python2 apps.
But default install will not include python2, just python3. But many apps still use python2, so it gets installed with that app.
Updated apps will specify python3, so they do not call python.

[rsteinmetz70112]

Python will be python2 as link. Not sure if they can change that as then it would break python2 apps.
But default install will not include python2, just python3. But many apps still use python2, so it gets installed with that app.
Updated apps will specify python3, so they do not call python.

That's how I understand it except:

# ls -ld python
lrwxrwxrwx 1 root root 9 Nov 23  2017 python -> python2.7
# ls -ld python2
lrwxrwxrwx 1 root root 9 Nov 23  2017 python2 -> python2.7
# ls -ld python3
lrwxrwxrwx 1 root root 9 Mar 23  2016 python3 -> python3.5

My remaining 16.04 LTS computers are all like this.

[dragonfly41]

Be aware that if on Ubuntu 16.04 python > 3.5 (such as 3.6) is installed, gnome-terminal ceases to launch. In Ubuntu 16.04 it depends on python 3.5 and does not run in 3.6. For this reason I now use virtualenv to switch between 2.7, 3.5, 3.6.

[rsteinmetz70112]

Be aware that if on Ubuntu 16.04 python > 3.5 (such as 3.6) is installed, gnome-terminal ceases to launch. In Ubuntu 16.04 it depends on python 3.5 and does not run in 3.6. For this reason I now use virtualenv to switch between 2.7, 3.5, 3.6.

As far as I can see python3.6 is not installed on my systems, python 3.5 is.

[rsteinmetz70112]

I've been reinstalling python packages. I finally got lucky. I reinstalled python3-pkg-resources and things seem to be working.

 apt install --reinstall python3-pkg-resources

Now to se if do-release-upgrade runs. Unfortunately it will be some time before I can test it.