[Python-Dev] Python environment registration in the Windows Registry

[Paul Moore]

On 3 February 2016 at 09:50, Glenn Linderman <v+python at g.nevcal.com> wrote:
> On 2/3/2016 12:15 AM, Alexander Walters wrote:
>
>> On a very personal note (like the rest of this wasn't my personal issues
>> with possibly making my life slightly more difficult), I would much rather
>> see python stop touching the registry all together - but I have no strong
>> argument for that.
>
> Me too. My opinions follow, some might call them arguments, strong or weak,
> some might call them foolishness.

I also would prefer that Python not use/need the registry. As far as I
know, in practical terms Python works just fine without the registry
entries being present, but I'd like it if that were formally supported
as an option for users. Obviously it means that tools that want to see
what Python versions are installed won't see such unregistered copies,
I'm fine with that (and I don't have a problem with leaving it up to
said tools as to whether they want to include ways to support using a
Python installation that's not in the registry).

Some issues with this proposal:

1. I don't like the way it states that Python distributions "must" set
keys. I'd rather that it were explicitly stated that a distribution
which sets no registry keys is entirely valid (with the obvious
implication that tools which scan the registry looking for installed
Python distributions won't be able to see such an installation).
2. It's not clear to me how alternative distributions will specify
their registry keys (or the fact that they don't use them). The
registry keys are built into the Python interpreter - this proposal
seems to imply that distributions that simply repackage the python.org
build will no longer be valid or supported, and instead anyone who
wants to produce a custom Python distribution (even private in-house
repackagings) will need to change the Python source and rebuild.
That's a pretty major change, and if that *is* the intent, then as a
minimum I'd say we need to provide compiler flags to let
redistributors specify their Company/Tag values (or say that they want
to omit registry use). And I'm still not happy that "repackage the
python.org binaries" has been removed as an option.

It's possible that the reason the above two points have been missed is
because the proposal focuses purely on "informational" registry data.
But Python also modifies sys.path based on the registry entries - and
possibly has other behavioural changes as well. The pywin32 package,
in particular, makes use of this (it's a feature of pywin32 that I
disagree with and I wish it didn't do that, but it does, and it's a
very widely used package on Windows). So ignoring this aspect of
Python's behaviour is a big problem. (Also, what changes will pywin32
need to make to correctly support being installed into non-python.org
distributions when this proposal is implemented?)

Paul