[Python-ideas] PEP: Distributing a Subset of the Standard Library

[Guido van Rossum]

Overall I think this is a good idea. I have one hit:

It seems that there are two possible strategies for searching the
.missing.py file:

1. (Currently in the PEP) search it at the same time as the .py file when
walking along sys.path.
  - Pro: prevents confusion when the user accidentally has their own
matching file later in sys.path.
  - Con: prevents the user from installing a matching file intentionally
(e.g. a 3rd party version).

2. After exhausting sys.path, search it again just for .missing.py files
(or perhaps remember the location of the .missing.py file during the first
search but don't act immediately on it -- this has the same effect).
  - Pro: allows user to install their own version.
  - Con: if the user has a matching file by accident, that file will be
imported, causing more confusion.

I personally would weigh these so as to prefer (2). The option of
installing your own version when the standard version doesn't exist seems
reasonable; there may be reasons that you can't or don't want to install
the distribution's version. I don't worry much about the danger of
accidental name conflicts (have you ever seen this?).


--Guido

On Mon, Nov 28, 2016 at 8:13 AM, Paul Moore <p.f.moore at gmail.com> wrote:

> On 28 November 2016 at 15:51, Tomas Orsava <torsava at redhat.com> wrote:
> > I believe I may have found the Windows curses implementation, it's called
> > PDCurses [0], and this website [1] appears to be distributing it under
> the
> > name `curses`.
>
> My apologies, I should have included a pointer. That is indeed the
> distribution I was thinking of.
>
> > Could some Windows user please check if compiling Python with the current
> > reference implementation [2] of this PEP indeed generates a
> > `curses.missing.py` file among the stdlib files? If so, we might
> consider
> > skipping the generation of the .missing.py file for the curses module on
> > Windows.
>
> I'll see if I can make some time to do the test. But as the change is
> to setup.py, and the Windows build uses Visual Studio project files to
> do the build, I expect that it won't generate missing.py files on
> Windows. In actual fact, that may be the simplest solution, to note
> that the build part of this change is restricted to Unix (non-Windows)
> platforms specifically. As there's no real concept of a "distribution
> version" of Python on Windows, it's probably not something that will
> be that important on that platform (and support for .missing.py files
> is there, it would just be necessary for distributors to manually
> create those files as needed).
>
> Paul
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-- 
--Guido van Rossum (python.org/~guido)
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