[Python-Dev] bug or a feature? (original) (raw)

Willem Broekema metawilm at gmail.com
Thu Jun 12 15:47:59 CEST 2008

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.

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