[Python-Dev] Disabling changing sys.argv[0] with runpy.run_module(...alter_sys=True)

[Gregory P. Smith]

On Tue, Feb 16, 2016 at 9:00 PM Mike Kaplinskiy <mike.kaplinskiy at gmail.com>
wrote:

> Hey folks,
>
> I hope this is the right list for this sort of thing (python-ideas seemed
> more far-fetched).
>
> For some context: there is currently a issue with pex that causes
> sys.modules lookups to stop working for __main__. In turns this makes
> unittest.run() & pkg_resources.resource_* fail. The root cause is that pex
> uses runpy.run_module with alter_sys=False. The fix should be to just pass
> alter_sys=True, but that changes sys.argv[0] and various existing pex files
> depend on that being the pex file. You can read more at
> https://github.com/pantsbuild/pex/pull/211 .
>
> Conservatively, I'd like to propose adding an argument to disable this
> behavior. The current behavior breaks a somewhat reasonable invariant that
> you can restart your program via `os.execv([sys.executable] + sys.argv)`.
>

I don't know enough about pex to really dig into what it is trying to do so
this is tangential to answering your question but:

sys.executable may be None. ex: If you're an embedded Python interpreter
there is no Python executable. It cannot be blindly used re-execute the
current process.

sys.argv represents the C main() argv array. Your inclination (in the
linked to bug above) to leave sys.argv[0] alone is a good one.

-gps

Moreover it might be user-friendly to add a `argv=sys.argv[1:]` argument to
> set & restore the full arguments to the module, where `argv=None` disables
> argv[0] switching.
>
> What do you think?
>
> Mike.
>
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