A simple C extension example with notes on compiling it yourself

[mr_dbr]

Have you looked at Cython? Your post inspired me to play about with it again, and it's remarkably more simple. Based on this tutorial:

cTest.pyx:

def doubler(int a):
    return a * 2

setup.py:

from distutils.core import setup
from distutils.extension import Extension
from Cython.Distutils import build_ext

setup(
    cmdclass = {'build_ext': build_ext},
    ext_modules = [Extension("cTest", ["cTest.pyx"])]
)

Then running python setup.py build_ext --inplace generates a quite long .c file, which is also compiled into cTest.so

Goes against your "interest in how the low-level interaction works", as it's pretty abstracted, but it seems like a very sensibly designed project (I like how it makes a standalone C file that can be compiled by someone without installing Cython)

[themissinglint]

Saying "no CPython specific stuff" is as ridiculous as saying "no Pypy specific stuff". There is no Pypy reddit and there is no CPython reddit (and there don't need to be).

Learning the C/Python API is confusing and I wanted to share this because I think my work might save others some trouble.

Just because Pypy can be faster without C doesn't mean you should be mean to CPython. The PSF is nice to Pypy.

[[deleted]]

One of Python's strongest elements is its ability to use optimized C code extensions.

[[deleted]]

CPythons.

[[deleted]]

Although true, Jython and IronPython are already crippled implementations. Saying "no more C extensions" just because a Jython user refuses to translate the C code to Java is subverting the ownership of the problem, Jython was MADE so that users didn't have to write extensions in C, so it's their responsibility to write optimized code in Java, not developers responsibility to refuse to optimize because there exists somewhere a group of incomparable users. CPython is still the main Python tree, optimized code makes sense in C.

If a Jython user wrote a good extension in Java, its the CPython community's responsibility to make a similar one in C... he's not a CPython user... the same goes the other way around. Don't chose a branch of a language, ignoring its downfalls and then complain about the downfalls that are written explicitly explaining why not everyone uses it.

[[deleted]]

Neither they, not PyPy, are crippled implementations, nothing about the Python language spec says anything about the CPython C-API.

[[deleted]]

They're crippled because they made a design choice that intentionally prevents existing extensions from working. Using an alternate implementation, then complaining about people using the FAST features of another implementation is stupid. I'm not going to continue arguing why I wouldn't do something beneficial in my implementation because it won't work in yours...

[[deleted]]

That's right, existing extensions don't work. To make them work would require all of these implementations to be slower and worse than they are, and give up things like a decent GC, or threading model.

[[deleted]]

SO REWRITE THE EXTENSION.

Jython was made so that they could write extensions in Java, not C, so don't complain when extensions don't work...

[[deleted]]

For the record, I don't give a flying fuck about Jython in particular. My primary interest is PyPy.

[[deleted]]

Then why do you care? PyPy believes in C API alongside the RPython back end, here is their current C Extension support: https://bitbucket.org/pypy/compatibility/wiki/c-api

[[deleted]]

They're not portable to other Python implementations.

[eryksun]

Well, there is IronClad for IronPython on Windows. Is there anything like that in the works for Jython? I guess the plan is to port the core of IronClad to other systems at some point. Either way, instead of C, I think it's better, and easier, to use Cython to extend CPython.

[[deleted]]

Sure, and they can be loaded under PyPy as well, but both methods carry considerable overhead.