On Wed, Nov 22, 2006 at 09:36:09AM +0100, Georg Brandl wrote:
> Terry Reedy schrieb:
> > "Brett Cannon" <[EMAIL PROTECTED]> wrote in message
> > news:[EMAIL PROTECTED]
> >
> > Why can't the fallback usage just pass the return value from __len__ to
> > bool() (forget the C function name) and return that result? It's just like
> > doing::
> >
> > def bool(obj):
> > try:
> > return obj.__bool__()
> > except AttributeError:
> > return bool(len(obj))
> > ------------
> >
> > If an object without __bool__ returned itself as its length, this would be
> > an infinite loop, at least in this Python version. Do we worry about
> > something so crazy?
>
> The length would have to be an integer, and this would have to be checked.
>
It looks like the regular checks are happening on __len__ methods
anyway so the explicit int check in slot_nb_bool is redundant.
This is the first time I've looked at the new slots in py3k so
feel free to correct. (using bool4.patch)
sprat:~/src/py3k-rw> ./python
Python 3.0x (p3yk:52823M, Nov 22 2006, 11:57:34)
[GCC 4.0.3 (Ubuntu 4.0.3-1ubuntu5)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> class A(object):
def __len__(self):
return -1
a = A()
print bool(a)
... ... ... >>> >>> Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: __len__() should return >= 0
>>>
-Jack
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