Hi!
On Thu, Apr 06, 2017 at 12:24:47PM +1000, Steven D'Aprano <st...@pearwood.info>
wrote:
> On Thu, Apr 06, 2017 at 02:30:06AM +0200, Oleg Broytman wrote:
>
> > I spent few days hunting
> > for a subtle bug caused by absent of unbound methods.
> > Painful. :-(
>
> I'm curious about this. What do you mean? Python 3 has unbound methods,
> they're just the original, unwrapped function:
>
> py> class K:
> ... def method(self, arg):
> ... pass
> ...
> py> K.method
> <function K.method at 0xb7cbd6a4>
I know.
> The only(?) functional difference between unbound methods in Python 2
> versus 3 is that in Python 2 they automatically do a type-check that
> `self` is an instance of the class.
The check was involved, yes. The bug I was hunting manifested itself
in PY3 with exceptions hinting that instead of `self` I've passed
`self.__class__`. In PY2 everything worked fine.
I found the problem in dynamically created methods. Someone
implemented them this way:
if PY2:
def createMethod(func, cls):
return types.MethodType(func, None, cls)
else:
def createMethod(func, cls):
return types.MethodType(func, None)
Hard to spot at the first glance what was the problem. Finally I grok
the problem and fixed the implementation for PY3 to
def createMethod(func, cls):
return func
> --
> Steve
Oleg.
--
Oleg Broytman http://phdru.name/ p...@phdru.name
Programmers don't die, they just GOSUB without RETURN.
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