pip/pip3 confusion and keeping up to date

[Jon Ribbens]

On 2023-11-02, Dieter Maurer <dieter at handshake.de> wrote:
> Chris Green wrote at 2023-11-2 10:58 +0000:
>> ...
>>So, going on from this, how do I do the equivalent of "apt update; apt
>>upgrade" for my globally installed pip packages?
>
> `pip list -o` will tell you for which packages there are upgrades
> available.
> `pip install -U ...` will upgrade packages.
>
> Be careful, though.
> With `apt`, you usually have (`apt`) sources representing a consistent
> package universe. Someone tests that package upgrades in this
> universe do not break other packages (in this universe).
> Because of this, upgrading poses low risk.
>
> `PyPI` does not guarantes consistency. A new package version
> may be incompatible to a previous one -- and with other
> package you have installed.
>
> I do not think that you would want to auto-upgrade all installed
> packages.

Indeed. What you're describing is a very unfortunate failing of pip.
'Upgrade' doesn't even follow requirements when you tell it what to
upgrade - e.g. if you do "pip install foo" and foo requires "bar<2"
so you end up with:

   Package                Version
   ---------------------- ---------
   foo                    1.0.0
   bar                    1.2.0

and then a new version 1.3.0 of bar comes out and you do
"pip install -U foo", pip will not upgrade bar even though it could
and should, because foo is already at the latest version so pip won't
even look at its dependencies.

Indeed there is no way of knowing that you should upgrade bar without
manually following all the dependency graphs. ("pip list -o" will tell
you there's a newer version, but that isn't the same - e.g. if the new
version of bar was 2.0.0 then "pip list -o" will list it, but you should
not upgrade to it.)

You can do "pip install -I foo", which will pointlessly reinstall foo
and then presumably upgrade bar as well, thus probably getting to the
right result via a rather roundabout route, but I'm not sure if that
does indeed work properly and if it is a reliable and recommended way
of doing things.