[Python-Dev] Changing the Division Operator -- PEP 238, rev 1.12

[Tim Peters]

Man, I'm having a hard time following this!  Perhaps people are talking
passed each other?

[Michael Hudson]
> It's a matter of interface, really.  It's certainly not at all
> technically hard.  Maybe:
>
>    compile(text, filename, symbol[, flags[, dont_inherit]])

Sounds good -- let's do it.

> I worry that saying "you don't inherit behaviour from surrounding code
> as soon as you pass a flag" might get really, really confusing at
> times.

I would too, but did someone suggest that?  Not me.  If someone did, they're
confusing issues to no good end.

[Guido]
> Occam sez: let's add the dont_inherit argument when we have found a
> real use for it.

It's trivial to add, impossible to work around its absence if necessary, and
is an inherent part of the problem space (as Michael said, the future-PEP
anticipated the problem).  It seems as simple as possible without leaving
problems unaddressed.

[Michael]
> There are two complementary sets of flags here:
>
> (1) The PyCF_* ones, defined in Include/pythonrun.h
> (2) The CO_* ones defined in Include/compile.h
>
> The proposed fourth argument to compile() should be a combination of
> the former set.
>
> I only use the latter to tell whether a __future__ statement was used
> in the text compiled (which is a bit horrible, but no better way
> springs to mind).

If there were a better way, we would have used it instead of the goofy CO_*
flags everywhere else too <wink>.

> There might be value in checking the flags passed to compile() anyway,
> but I can't see it being dangerous.

It's so easy to make this bulletproof that there's no point discussing
whether it *should* be made bulletproof.  I'll see to it that it's
bulletproof in the end, so if it's a hangup don't worry about it now.

[Guido]
> (I think I may have been confused by your original patch, which AFAICR
*did*
> manipulate the co_flags field of the code object, which contains the CO_*
flags.

Right, it did, and the newer scheme is safer.