python 3 problem: how to convert an extension method into a class Method
__peter__ at web.de
Tue Feb 26 21:54:29 CET 2013
Ethan Furman wrote:
> On 02/26/2013 09:21 AM, Robin Becker wrote:
>> In python 2 I was able to improve speed of reportlab using a C extension
>> to optimize some heavily used methods.
>> so I was able to do this
>> class A:
>> def method(self,...):
>> from extension import c_method
>> import new
>> A.method = new.instancemethod(c_method,None,A)
>> and if the try succeeds our method is bound as a class method ie is
>> unbound and works fine when I call it.
>> In python 3 this doesn't seem to work at all. In fact the new module is
>> gone. The types.MethodType stuff doesn't seem to work.
>> Is there a way in Python 3.3 to make this happen? This particular method
>> is short, but is called many times so adding python wrapping layers is
>> not a good way forward.
> Dumb question, but have you tried just assigning it? In Py3 methods are
> just normal functions...
> class A():
> A.method = c_method
The problem is that functions implemented in C don't support the descriptor
protocol (they don't have a __get__() method). So
>>> from math import sqrt
>>> class A(int):
>>> A.c = sqrt
>>> A.py = lambda self: sqrt(self)
>>> a = A(42)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: sqrt() takes exactly one argument (0 given)
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