[Python-Dev] Non-string keys in namespace dicts
Phillip J. Eby
pje at telecommunity.com
Tue Dec 4 07:20:32 CET 2007
At 10:17 PM 12/3/2007 -0700, Neil Toronto wrote:
>Phillip J. Eby wrote:
> > Actually, you're missing the part where such evil code *can't* muck
> > things up for class dictionaries. Type dicts aren't reachable via
> > ordinary Python code; you *have* to modify them via setattr. (The
> > __dict__ of types returns a read-only proxy object, so the most evil
> > rich compare you can imagine still can't touch it.)
>Interesting. But I'm going to have to say it probably wouldn't work as
>well, since C code can and does alter tp_dict directly. Those places in
>the core would have to be altered to invalidate the cache.
Eh? Where is the type dictionary altered outside of setattr and
> There's also
>the issue of extensions, which so far have been able to alter any
>tp_dict without problems.
Do you have any actual examples?
Believe me, I'm the last person to suggest removing useful hack, er,
hooks. :) But I don't think that type __dict__ munging is actually
common at all.
>It'd also be really annoying for a class to
>have to notify all of its subclasses when one of its attributes changed.
It's not all subclasses - only those subclasses that don't shadow the
attribute. Also, it's not necessarily the case that notification
would be O(subclasses) - it could be done via a version counter, as
in your approach. Admittedly, that would require an extra bit of
indirection, since you'd need to keep (and check) counters for each descriptor.
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