[Python-Dev] issue5578 - explanation
Guido van Rossum
guido at python.org
Thu Apr 2 23:18:30 CEST 2009
On Thu, Apr 2, 2009 at 2:16 PM, Chris Withers <chris at simplistix.co.uk> wrote:
> R. David Murray wrote:
>> On Wed, 1 Apr 2009 at 13:12, Chris Withers wrote:
>>> Guido van Rossum wrote:
>>>> Well hold on for a minute, I remember we used to have an exec
>>>> statement in a class body in the standard library, to define some file
>>>> methods in socket.py IIRC.
>>> But why an exec?! Surely there must be some other way to do this than an
>> Maybe, but this sure is gnarly code:
>> _s = ("def %s(self, *args): return self._sock.%s(*args)\n\n"
>> "%s.__doc__ = _realsocket.%s.__doc__\n")
>> for _m in _socketmethods:
>> exec _s % (_m, _m, _m, _m)
>> del _m, _s
> I played around with this and managed to rewrite it as:
> from functools import partial
> from new import instancemethod
> def meth(name,self,*args):
> return getattr(self._sock,name)(*args)
> for _m in _socketmethods:
> p = partial(meth,_m)
> p.__name__ = _m
> p.__doc__ = getattr(_realsocket,_m).__doc__
> m = instancemethod(p,None,_socketobject)
> Have I missed something or is that a suitable replacement that gets rid of
> the exec nastiness?
That code in socket.py is much older that functools... I don't know if
the dependency matters, probably not.
But anyways this is moot, the bug was only about exec in a class body
*nested inside a function*.
--Guido van Rossum (home page: http://www.python.org/~guido/)
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