python 3 problem: how to convert an extension method into a class Method
Peter Otten
__peter__ at web.de
Tue Feb 26 13:38:44 EST 2013
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,...):
> ....
>
>
> try:
> from extension import c_method
> import new
> A.method = new.instancemethod(c_method,None,A)
> except:
> pass
>
> 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.
>
> If the above cannot be made to work (another great victory for Python 3)
> then is there a way to bind an external method to the instance without
> incurring too much overhead.
Hm, according to my random measurement your clever approach incurs more
overhead than the straight-forward way that continues to work in Python 3:
$ python -m timeit -s 'from new import instancemethod
> from math import sqrt
> class A(int): pass
> A.m = instancemethod(sqrt, None, A)
> a = A(42)
> ' 'a.m()'
1000000 loops, best of 3: 0.5 usec per loop
$ python -m timeit -s 'from math import sqrt
> class A(int):
> def m(self):
> return sqrt(self)
> a = A(42)
> ' 'a.m()'
1000000 loops, best of 3: 0.473 usec per loop
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