[Python-Dev] defaultdict proposal round three (original) (raw)

Greg Ewing greg.ewing at canterbury.ac.nz
Tue Feb 21 10:51:20 CET 2006

Guido van Rossum wrote:

It's quite tricky to implement a fully transparent wrapper that supports all the special methods (setitem etc.).

I was thinking the wrapper would only be a means of filling the dict -- it wouldn't even pretend to implement the full dict interface. The only method it would really need to have is getitem.

The semantics of defaultdict are crystal clear. contains(), keys() and friends represent the actual, current keys.

If you're happy with that, then I am too. I was never particularly attached to the wrapper idea -- I just mentioned it as a possible alternative.

Just one more thing -- have you made a final decision about the name yet? I'd still prefer something like 'autodict', because to me 'defaultdict' suggests a type that just returns default values without modifying the dict. Maybe it should be reserved for some possible future type that behaves that way.

Also, considering the intended use cases (accumulation, etc.) it seems more accurate to think of the value produced by the factory as an 'initial value' rather than a 'default value', and I'd prefer to see it described that way in the docs. If that is done, having 'default' in the name wouldn't be so appropriate.

Greg

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