[Python-Dev] bug or a feature?

[Willem Broekema]

On Thu, Jun 12, 2008 at 2:56 PM, Carl Friedrich Bolz <cfbolz at gmx.de> wrote:
> Of course attribute name lookups are affected, because you can have a
> non-string key that has a __hash__ and __eq__ method to make it look
> sufficiently like a string to the dict. Then the attribute lookup needs
> to take these into account. This makes a method cache implementation
> much more complex, because suddenly arbitrary user code can run during
> the lookup and your classes (and thus your method caches) can change
> under your feed during the lookup. In this situation getting the corner
> cases right is very hard.

I fully agree with this assessment: the theoretical possibilities make
attribute handling very hairy.
Note that besides non-strings, also user-defined subclasses of string
can have their own hash/eq logic.

If namespace keys and attributes could be locked down to only be
regular strings, not of another type and not a string subclass
instance, then implementing attributes becomes a lot less hairy, and
optimizations much more straightforward.

- Willem (CLPython)