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

Brett Cannon brett at python.org
Wed Feb 17 13:44:52 EST 2016


On Tue, 16 Feb 2016 at 20:59 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)`.
> 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?
>

This probably is best served as a feature request on bugs.python.org since
it's not asking for some massive change or new feature but just a minor
tweak to a module.
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