Uninstall python 2.7 fails - alternative dependencies

Uninstall python 2.7 fails - alternative dependencies

[Doug Henderson]

I attempted to remove all packages related to Python 2.7 from my
cygwin installation.

I am unable to remove four packages.

python2
python27
python27-pip
python27-setuptools

There are over 500 packages that require python2 and over 700 packages
which depend2 on python2.

There are also around 90 packages that refer to both python2 and
python3 packages. I have many of these packages installed. I suspect
that at least some of these actually require either python2 or
python3, but do not require both.

To assist in supporting this kind of requirement, is there a way to
create a package whose requirements are resolved by either of several
other packages?

For instance, could we have a package e.g. python-alternatives, that
when required is satisfied by either python2 or python3. This
mechanism might be useful for dealing with any set of packages that
work with the alternatives system.

Thanks for your consideration,
Doug

-- 
Doug Henderson, Calgary, Alberta, Canada - from gmail.com

Re: Uninstall python 2.7 fails - alternative dependencies

[Adam Dinwoodie]

On Tue, 2 Mar 2021 at 17:33, Doug Henderson via Cygwin wrote:
> To assist in supporting this kind of requirement, is there a way to
> create a package whose requirements are resolved by either of several
> other packages?
>
> For instance, could we have a package e.g. python-alternatives, that
> when required is satisfied by either python2 or python3. This
> mechanism might be useful for dealing with any set of packages that
> work with the alternatives system.

Yes, this function already exists in the form of the "provides" line
in setup.hint files, discussed at
https://cygwin.com/packaging-hint-files.html, although I don't believe
the function is widely used.

Per that page: If you think that another package has an incorrect
dependency list, send email to cygwin-apps noting that fact.

Adam

Re: Uninstall python 2.7 fails - alternative dependencies

[Marco Atzeri]

On 02.03.2021 18:32, Doug Henderson via Cygwin wrote:
> I attempted to remove all packages related to Python 2.7 from my
> cygwin installation.
> 
> I am unable to remove four packages.
> 
> python2
> python27
> python27-pip
> python27-setuptools

Question:
you can not remove because they are cross dependent or because they
are pulled by other packages ?

> There are over 500 packages that require python2 and over 700 packages
> which depend2 on python2.

much less

$ cygcheck-dep -S -q -n python2| wc -w
124

$ cygcheck-dep -S -q -n python27| wc -w
145

and most are python2-* or python27-* packages

> There are also around 90 packages that refer to both python2 and
> python3 packages. I have many of these packages installed. I suspect
> that at least some of these actually require either python2 or
> python3, but do not require both.

are you sure ? May be you are counting different releases ?
Usually they should pull only one version of python.

> To assist in supporting this kind of requirement, is there a way to
> create a package whose requirements are resolved by either of several
> other packages?

Not that I am aware

> For instance, could we have a package e.g. python-alternatives, that
> when required is satisfied by either python2 or python3. This
> mechanism might be useful for dealing with any set of packages that
> work with the alternatives system.
> 
> Thanks for your consideration,
> Doug
>