PEP 704 - Require virtual environments by default for package installers

[CAM-Gerlach]

@rgommers

A name for a default virtual env - chosen to be .venv. This is fairly similar to PEP 582’s __pypackages__.

Right, this part of this PEP merely proposes a standard name for an in-tree virtual env, which is essentially harmless from Conda’s perspective (whereas it is item 2 that of course presents the major challenges and concerns with this PEP, as discussed here). But it’s not totally comparable to what PEP 582 is proposing; there the default name is merely incidental to the behavior changes for installers and for Python itself, which is more analogous to the problems with the previous proposal to separate Conda and pip-installed packages into separate prefixes. There’s some more detail in my reply to that thread (to avoid straying too far OT on this one):

PEP 582 - Python local packages directory

A couple of the potential issues I can think of for Conda users include: The presence of a __pypackages__ dir meaning that installers will install into it by default, rather than the active environment, which has the same issues as the parallel pip and conda prefixes proposed and discussed above, along with it meaning whether pip installs into a Conda env or __pypackages__ depends on the user’s CWD, and impossible for Conda to manage Python adds it to sys.path and any packages here will shadow…

@pf_moore

People will still be able to install into their Windows system environment (because the Windows Python installers don’t set EXTERNALLY-MANAGED) and maybe also into conda base environments or spack environments, depending on what those distributors decide to do about PEP 668.

For Conda, it would indeed seem to be good enough as far as this department is concerned—see conda/conda#12245, which @pradyunsg actually opened as a result of me suggesting the potential benefits for Conda of this PEP covering Conda envs too, i.e.

@h-vetinari

Unless “virtual env” is loosened to something that can be filled by a conda environment, then it would actually help a lot IMO, because always[1] having (some form of) an environment would be very helpful IMO.

As Conda would be able to achieve the same effect with EXTERNALLY-MANAGED, just under it’s control, this PEP isn’t needed to achieve the same effect (as Pradyun himself pointed out to me).