FWIW, one of my intro students just yesterday asked about this:
Is there a way to call a function in a python file directly from the
command line?
I have no idea what their programming background is, or why they expected
that to be possible, but there you go -- at least one newbie expected it to
be possible :-)
However: This was literally class number one -- I had not yet showed them
the "if __name__ == '__main__':" idiom yet.
Also, I'm pretty sure this student's expectation was that there would not
have to be anything special about the function (except maybe taking only
string arguments?) -- so it's probably not a good idea to try to solve
that use case anyway.
But that was the first time I was ever asked that question -- and here it
is on python-ideas -- quite a coincidence!
-CHB
On Tue, Oct 20, 2020 at 11:16 PM Paul Sokolovsky <pmis...@gmail.com> wrote:
> Hello,
>
> On Wed, 21 Oct 2020 00:24:47 -0400
> Michael Smith <mich...@smith-li.com> wrote:
>
> > On Tue, Oct 20, 2020 at 23:43 Guido van Rossum <gu...@python.org>
> > wrote:
> >
> > > The ‘if __name__…’ idiom makes one function special. Hm... So if the
> > > module has that, will that main() still be called with your
> > > proposal? I.e., is __name__ still ‘__main__’?
> > >
> >
> > Perhaps not. If __name__ were still '__main__' and calling the
> > function implied importing the module, then anything in `if __name__
> > == '__main__'` would still get run. I think that would be
> > inconvenient for folks.
>
> Alternative valuation is that your proposal is inconvenient to folks,
> as it leaves too many gaps. Which, as it seems, you're eager to
> bravely patch, but that does/will lead to only more confusion.
>
> > I think __name__ should be the module name in the context of the
> > module, and the function name in the context of the function, in this
> > case.
>
> __name__ is the name of the module. Or, as a special exception, it's
> "__main__" for a module directly invoked as a script or via "-m"
> switch.
>
> There's no need to complicate it any further (it's already complicated
> enough; my bet that half of Python users won't be able to formulate it
> like above by heart).
>
>
> Back to the original proposal, there's no general need to invoke
> an arbitrary function in an arbitrary module. That just makes no sense,
> as most functions depend on context.
>
> If *you* need that, then, besides other options you mentioned in
> your original mail, it's trivial to write a module which will do it for
> you, like:
>
> python -m my_super_invocator module:thunk
>
>
> Actually, if you look on PyPI, I bet you'll find a few like that.
>
> >
> > On Tue, Oct 20, 2020 at 20:32 Michael Smith <mich...@smith-li.com>
> > wrote:
> > >
> > >>
> > >>
> > >> On Tue, Oct 20, 2020 at 23:12 Guido van Rossum <gu...@python.org>
> > >> wrote:
> > >>> On Tue, Oct 20, 2020 at 8:06 PM Michael Smith
> > >>> <mich...@smith-li.com> wrote:
> > >>>
> > >>>> On Tue, Oct 20, 2020 at 10:19 PM Guido van Rossum
> > >>>> <gu...@python.org> wrote:
> > >>>> >
> > >>>> > I think it would be a tad more convincing if there was a way
> > >>>> > to pass
> > >>>> arguments too (even if just a list of strings). At the very
> > >>>> least extra arguments should end up in sys.argv[1:].
> > >>>>
> > >>>> Could python -m 'module:thunk' have exactly the same behavior
> > >>>> with respect to arguments as `python3.8 -m module` does today?
> > >>>>
> > >>>> ```
> > >>>> $ cat bar.py
> > >>>> import pprint, sys
> > >>>>
> > >>>> def thunk():
> > >>>> pprint.pprint(sys.argv)
> > >>>>
> > >>>> if __name__ == "__main__":
> > >>>> thunk()
> > >>>>
> > >>>> $ python3.8 -m bar -- -1 --two --three=3
> > >>>> ['/Users/michael/bar.py', '--', '-1', '--two', '--three=3']
> > >>>> ```
> > >>>>
> > >>>> So then with the same bar.py, `python -m bar:thunk -- -2 --three
> > >>>> --four=4` would print `['/Users/michael/bar.py', '--', '-1',
> > >>>> '--two', '--three=3']`. I like this better than my previous
> > >>>> suggestion to shorthand python -c.
> > >>>>
> > >>>
> > >>> Actually it should print the same except for sys.argv[0]. (We
> > >>> could argue about what sys.argv[0] should be.)
> > >>>
> > >>>
> > >>>> > Then again, presumably the function must be specially crafted
> > >>>> > for
> > >>>> this usage. Why can't you just specially craft a module's main()?
> > >>>>
> > >>>> I'm not sure I know what you mean by "specially crafted", other
> > >>>> than the function only needs not require any formal parameters.
> > >>>> It doesn't need to be special-er than that. It can handle args
> > >>>> via sys.argv, as you suggested. Most of the `main` functions I
> > >>>> write today are just like that.
> > >>>>
> > >>>
> > >>> Okay, so this is just a way to choose an alternative main()
> > >>> function.
> > >>
> > >> Am I missing something important here? What's special about naming
> > >> a function "main"? Don't you still have to do something else to
> > >> invoke it from the cli, such as calling it expressly in the module
> > >> or pointing console entry points to it?
> > >>
> > >> ```
> > >> $ echo 'def main(): print("hi")' > xyz.py
> > >> $ python -m xyz
> > >> <no output>
> > >> $
> > >> ```
> > >>
> > >> I'm kind of meh at this point, I'll leave it to the usual
> > >> crowd. :-)
> > >>>
> > >>
> > >> I appreciate the engagement you've given this already. :)
> > >>
> > >> --
> > >>> --Guido van Rossum (python.org/~guido)
> > >>> *Pronouns: he/him **(why is my pronoun here?)*
> > >>> <
> http://feministing.com/2015/02/03/how-using-they-as-a-singular-pronoun-can-change-the-world/
> >
> > >>>
> > >> --
> > > --Guido (mobile)
> > >
>
>
>
> --
> Best regards,
> Paul mailto:pmis...@gmail.com
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--
Christopher Barker, PhD
Python Language Consulting
- Teaching
- Scientific Software Development
- Desktop GUI and Web Development
- wxPython, numpy, scipy, Cython
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