On Tue, Feb 16, 2016 at 9:42 PM, Gregory P. Smith <greg at krypto.org> wrote: > > 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: > Sorry about that - a pex file is kind of like a relocatable virtualenv in one zip file. When it runs, it first executes some pex-specific code to extract packages (.egg, .whl) and add them to sys.path before running the actual user code. It's conceptually similar to a fat .jar file in JVM projects - all you need is `python`/`java` and all the code is in one file. > 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. > I was originally going to argue for getting rid of the feature entirely, but if runpy is to live up to the promise of being exactly the same as `python -m XXX yyy zzz`, it needs to be there. IMO it's bad form to depend on sys.argv[0] for anything but presentation purposes - usage messages and the like. It's hard to justify breaking compatibility for that though - unfortunately the runpy interface isn't pliable enough to really reimplement or unimplement this feature, and doing it by hand is...painful. You can also make an argument that `python runmodule.py module a b` and `python -m module a b` should be _exactly_ the same output, especially if `runmodule.py` is implementing something pass-through like profiling, coverage or tracing. A nicer interface might be some sort of callback to "do whatever you want before the module is executed", but that might be overkill. > > -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. >> >> _______________________________________________ >> Python-Dev mailing list >> Python-Dev at python.org >> https://mail.python.org/mailman/listinfo/python-dev >> Unsubscribe: >> https://mail.python.org/mailman/options/python-dev/greg%40krypto.org > > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://mail.python.org/pipermail/python-dev/attachments/20160216/f43dba9b/attachment.html>
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