[Python-Dev] VM and Language summit info for those not at Pycon (and those that are!)

Greg Ewing greg.ewing at canterbury.ac.nz
Mon Mar 21 06:42:37 CET 2011

Guido van Rossum wrote:
> Cython feels much less
> mature than CPython; but the latter should only have dependencies that
> themselves change even slower than CPython.

You might be slightly more amenable to Pyrex, then, which
changes at a much more conservative pace!

They appear superficially similar, but there is a difference
in underlying philosophy. Pyrex makes no claim to be a
Python compiler; rather, it's a tool for bridging between
the Python and C worlds. As such, strict adherence to
Python syntax and semantics, or supporting all Python
features, or performing heroic optimisations on pure
Python code, are not design goals.

So it wouldn't make sense to try to compile any of the
pure Python parts of the stdlib with Pyrex. However, it
could make sense to use it for some of the modules
currently written in C, or for future modules that
would otherwise be written in C, to make them easier to
write, read and maintain.

Think of it as a tool for writing modules in C without
having to worry about reference counts or exception

If you think you might seriously consider using Pyrex,
I could translate a module or two from the stdlib so
you can see how the code might look.

> I also am unclear on how
> exactly you're supporting the different semantics in Python 2 vs. 3
> without recompiling.

I gather that Cython generates code with a lot of #ifs
for doing things differently depending on the Python

I haven't decided exactly how to handle Python 3 in
Pyrex yet, but I have some ideas. I'm not sure whether
it will generate dual-version C files or not. It
probably wouldn't matter much for stdlib usage, though,
because it only needs to generate C code good enough
for a particular release of Python.


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