Finding it very difficult to move pyexiv2 code from Python 2 to Python 3

[Chris Green]

Cameron Simpson <cs at cskk.id.au> wrote:
> On 19Aug2020 08:53, Chris Green <cl at isbd.net> wrote:
> >I have quite a lot of things installed with pip, however I've never
> >had this problem with dependencies before.  Adding to the fun is that
> >my system has still got Python 2 as the default Python so I have to
> >run pip3 explicitly to get Python 3 code.
> 
> My approach to this is to have a personal venv based on a modern Python3 
> and put its bin near the front of my $PATH. The pip and python come from 
> it. But I tend to type "pip3" anyway - still the pip from my venv.
> 
> >Maybe I should bite the bullet and make Python 3 the default Python
> >and see what falls over as a consequence.
> 
> Don't change the system default Python - many system scripts rely on 
> that and may break. If an OS update changes it, it should also update 
> all the dependent scripts and so be ok, but an ad hoc change of only 
> part of the system is asking for trouble.
> 
It's actually more subtle and complicated than the OS changing or not
changing the default Python version.  There are quite a lot of
questions about exactly this on the Ubuntu lists.  All the OS python
code in Ubuntu 20.04 is now Python 3 but there are some other things
which I have installed (such as Mercurial) which still depend on
Python 2.  One can see what is affected by doing:-

    $ sudo apt remove python2 --simulate

This shows a mixture of old (and no longer needed) libraries that
would go with Python 2 but it also shows some things like Mercurial
that I need.

So Python 2 stays for the moment.

-- 
Chris Green
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