[Pyrex] C versus Python access

[David McNab]

On Tue, 2007-10-30 at 15:45 -0700, Robert Bradshaw wrote:
> Funny you should ask, there's a new call type in Cython that does  
> exactly this.
8><
>      cpdef int area(self):
>          return self.width * self.height
> 
> It will create a (python-accessible) def function that wraps the  
> cpdef function, but if the call is made on a Rect object, e.g.
> 
> cdef Rect my_rect = Rect(3,4)
> print my_rect.area()
> 
> then the fast c method is called. The result is much cleaner code and  
> no messy wrapper functions with different names. On top of that it is  
> still overrideable, if you have a cdef subclass, override it with a  
> cpdef method, and if you (or someone using your code) creates a  
> python subclass, they can override it with a normal python method  
> (which won't be as fast of course, but will get called even if the  
> call is made from pyrex). The overhead is extremely small. This is an  
> extremely new functionality and needs to be better documented. (It  
> used to be called rdef by the way.)

Hi Robert,

Thanks for switching me on. I'm trying out Cython - so far, so good. I
could end up defecting for good.

Is there an up-to-date list of the Cython/Pyrex differences anywhere? I
looked on the Cython website and wiki, but no such list jumped out at
me.

Are there any other goodies apart from cpdef?

Cheers
David

> 
> 
> On Oct 30, 2007, at 3:09 PM, David McNab wrote:
> 
> > Hi folks,
> >
> > I'm trying to optimise a pile of Pyrex code, mainly by using C method
> > calls wherever possible - but trying to keep the more important  
> > methods
> > accessible from Python.
> >
> > To give a simple and very silly example:
> >
> >         cdef class Rect:
> >
> >             cdef readonly int width, height
> >
> >             def __init__(self, int width, int height):
> >                 self.width = width
> >                 self.height = height
> >
> >             cdef public int _area(self):
> >                 return self.width * self.height
> >
> >             def area(self):
> >                 return self._area()
> >
> > Here, I've defined a C method '_area', which can be called efficiently
> > from Pyrex code without all the argument parsing, getattr, python  
> > object
> > calls etc. Also, Python method 'area' is a thin wrapper around  
> > '_area()'
> > which makes '_area()' available to Python callers.
> >
> > In this approach, I'm trying to get the best of both worlds - methods
> > which can be called efficiently at C level, but are also wrapped and
> > exposed to Python callers.
> >
> > Is there a better way to shave off CPU cycles?
> >
> > Cheers
> > David
> >
> >
> >
> >
> > _______________________________________________
> > Pyrex mailing list
> > Pyrex at lists.copyleft.no
> > http://lists.copyleft.no/mailman/listinfo/pyrex
> 
> 
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