[Python-ideas] {Python-ideas] C-API exposure

Guido van Rossum guido at python.org
Tue Mar 29 20:47:28 CEST 2011

On Tue, Mar 29, 2011 at 11:30 AM, Eric Snow <ericsnowcurrently at gmail.com> wrote:
> Certainly neither the new builtins nor the "pure" Python extrapolations
> would be portable.  And I wasn't suggesting that they be exposed in the
> builtins module, but rather in their own module.  By nature they would be
> implementation specific.  However, they would be as insightful as poking
> around the C-API is (which I found to be very), but in Python.
> As far as Cython goes, I am not terribly familiar with it.  However, I think
> it is a sort of opposite.  Cython seems to push Python down into C.  The
> C-API builtins would push the C into Python (that doesn't sound good).
> Regardless, I think doing this would take too much work to be worth it.  But
> I did want to get the idea out there.  I starting thinking about this when I
> was messing around with exec_closure.    While it has proven superfluous,
> working on it exposed me to all the pieces in the C-API that do not have
> counterparts in Python.  Things like cell objects.  There are things in
> there that you can emulate, but not in an explicit way (like
> PyEval_EvalCodeEx).
> It seems like as time has gone by, more of the internals have been exposed,
> like the AST module, the types module, metaclasses, the dis module, and
> others.  Certainly these are not run-of-the-mill modules, and neither would
> this be.  Those others have come about as needs have presented.  I expect
> that will continue to be the case.  The idea here was to skip to the chase
> and just expose the whole API.

Well people already do this using ctypes...

> One of my key questions is, what are the dangers in doing so?  Security?
>  Risk of fostering hacks?  More people relying on implementation specific
> details?  Enabling code that is incongrous with the Python vision?  These
> are questions to which I am trying to find answers as I dive into the
> python-dev world.  I appreciate the feedback by the way!

Any or all of the above, probably, depending on the specific API
you're considering...

You seem to have ignored my suggestion to think about how this would
work in other Python interpreters.

Also many of the C APIs have subtle reference count behavior -- you
don't want to have to worry about refcounting bugs *in your Python

--Guido van Rossum (python.org/~guido)

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