On 4/30/07, Barry Warsaw <[EMAIL PROTECTED]> wrote:
> On Apr 27, 2007, at 1:10 PM, Jim Jewett wrote:
> > On 4/27/07, Barry Warsaw <[EMAIL PROTECTED]> wrote:
> >> Finally, I'm concerned with the "weight" of adding ABCs to all the
> >> built-in types.
> > What if the builtin types did not initially derive from any ABC, but
> > were added (through an issubclass override) when the abc module was
> > imported?
> That would allow for some unfortunately global side-effects. Say I
> happen to import your library that imports abc. Now all the built-in
> types in my entire application get globally changed. I'm also not
> sure how you'd implement that.
I don't see how these side-effects could ever be detected, except to
the extent that issubclass overrides are inherently dangerous.
I see it something like
# module abc.py
class Integer()...
...
Integer.register(int)
Integer.register(long)
After that, int (and long) are changed only by the addition of an
extra reference count; their __bases__ and __mro__ are utterly
unchanged. But
isinstance(int, Integer)
is now True. Yes, this is global -- but the only way to detect it is
to have a reference to Integer, which implies having already relied on
the ABC framework.
-jJ
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