[Python-3000] Metaclasses in Py3K (original) (raw)

Talin talin at acm.org
Mon Dec 18 08:46:18 CET 2006

Greg Ewing wrote:

The main use case for all this seems to be that some metaclasses would like to know the order in which attributes were defined. So here's an alternative proposal: Leave the syntax the way it is, and always use a specialised dict that remembers the order of definition. The metaclass can then use that information or ignore it as it wishes.

I'm not sure that this is the only use case for overriding the locals() dict at class definition time, but at the moment I can't think of any others. So I won't try to struggle too hard against this idea.

Do you have a specific proposal as to how the information about the ordering of definitions could be extracted? I'm assuming that there would be an extra attribute that would return a list of keys in the order that they were defined. One tricky part here is if the same key were to be defined twice (i.e. being overwritten the second time), we probably would only want it to appear once, probably at the location where it was defined last.

-- Talin

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