[Python-Dev] Using Cython for standard library? (original) (raw)

Stefan Behnel stefan_ml at behnel.de
Tue Nov 4 20:08:06 CET 2008

Gerhard Häring wrote:

Cython is still being worked on (intensively, it seems). Bundling it with Python means deciding on a particular version probably for an entire major release lifecycle (use Cython x.y.{newest} for Python 2.7, for example).

Yes, that is definitely an issue. Cython is heavily being worked on, a lot of features were implemented this summer. This means that even slightly different Cython versions can generate heavily different code.

The project has made inclusion into Python's stdlib a goal right from the beginning. However, it is not currently clear when we will reach a suitable level of Python language compliance to make a language/feature freeze. Note that this only means a state where we decide to keep new features out. What's in there now will not go away, so existing Cython code is pretty much future proof (it even runs on Py3 already :).

I would love to see the option to write the lower levels in something other than C,

Well, Cython is definitely an option for that.

Absolutely. That's why I tried to reimplement pysqlite in something easier to maintain than handwritten Python C API. There's a ctypes-based version in its Mercurial repository that's good enough to be used from PyPy now. And a started Cython-based one.

ctypes makes sense for projects that do not require a high-speed interface, i.e. if you do major things behind the interface and only call into it from time to time, choosing ctypes will keep your code more portable without requiring a C compiler. However, if speed matters then it's hard to beat Cython even with hand-written C code.

but obviously any choice would have to be a good one. [...] So, the question I see isn't if Cython should be allowed for standard library modules, but if the landscape of such solutions is at a point that any of them is ready to be committed to.

Well, we had reports that existing, non-trivial C modules could be rewritten in Cython within a few days. But even if you are only talking about new modules that get added to the stdlib, all you really need to become independent of a specific Cython version is a good test suite for your code to make sure it keeps working as expected when you update your compiler.

Stefan

More information about the Python-Dev mailing list