Extending Python: rewriting a single method in C

[Jeff Epler]

On 12 Mar 2001 11:13:51 +0000, Jacek Generowicz
 <jmg at ecs.soton.ac.uk> wrote:
>I have an object-oriented numerical code written in Python. It has
>come to the stage where the speed of the code is seriously impeding
>progress. Profiling reveals (surprise, surprise) that most of the time
>is spent in only 2 methods.
>
>Is there any way of re-writing just these methods in C ?

It's easy to write a function in C.  Other posters have mentioned references 
to documentation about doing this.

However, you cannot make a builtin function be a method of a class/instance.
Instead, you could write:

from cmodule import fast_a, fast_b

class fastKlass(Klass):
	def a(self, int1, int2):
		fast_a(self, int1, int2)
	def b(self, int1, int2):
		fast_b(self, int1, int2)

In fast_a and fast_b, you can get arguments by using the ParseTuple string
"(Oii)" and then use PyObject_SetAttrString and PyObject_GetAttrString
to store or retrieve attributes (including, if necessary, instance
methods) from the instance by their name.

Note that if there are *many* calls to the method, rather than each
invocation taking a large amount of time, then this approach is not
going to gain you much, since it actually *increases* the function-call
overhead.

Jeff