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<div dir="ltr"><div class="gmail_extra"><div class="gmail_quote">On Tue, Feb 16, 2016 at 9:42 PM, Gregory P. Smith <span dir="ltr"><<a href="mailto:greg@krypto.org" target="_blank">greg@krypto.org</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><br><div class="gmail_quote"><span class=""><div dir="ltr">On Tue, Feb 16, 2016 at 9:00 PM Mike Kaplinskiy <<a href="mailto:mike.kaplinskiy@gmail.com" target="_blank">mike.kaplinskiy@gmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">Hey folks,<div><br></div><div>I hope this is the right list for this sort of thing (python-ideas seemed more far-fetched).</div><div><br></div><div>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 <a href="https://github.com/pantsbuild/pex/pull/211" target="_blank">https://github.com/pantsbuild/pex/pull/211</a> .</div><div><br></div><div>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)`.</div></div></blockquote><div><br></div></span><div>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:</div></div></div></blockquote><div><br></div><div>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.</div><div><br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div class="gmail_quote"><div><br></div><div>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.</div><div><br></div><div>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.</div></div></div></blockquote><div><br></div><div>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.</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div class="gmail_quote"><div><br></div><div>-gps</div><div><br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><span class=""><div dir="ltr"><div>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.</div><div><br></div><div>What do you think?</div><div><br></div><div>Mike.</div><div><br></div></div></span>
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