[Python-Dev] PEP 560: bases classes (original) (raw)
Nick Coghlan ncoghlan at gmail.com
Wed Nov 15 10:37:06 EST 2017
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On 16 November 2017 at 00:20, Jim J. Jewett <jimjjewett at gmail.com> wrote:
I think the following will happen:
"NewList[int]" will be evaluated, and classgetitem called, so that the bases tuple will be (A, GenericAlias(NewList, int), B) # (A) I think mroentries gets called with the full tuple, # instead of just the object it is found on. # (B) I think it is called on the results of evaluating # the terms within the tuple, instead of the original # string representation. tmp = mroentries(A, GenericAlias(NewList, int), B) # (C) I think mroentries returns a replacement for # just the single object, even though it was called on # the whole tuple, without knowing which object it # represents. bases = (A, tmp, B)
My understanding of the method signature:
def __mro_entries__(self, orig_bases):
...
return replacement_for_selfMy assumption as to the purpose of the extra complexity was:
- given orig_bases, a method could avoid injecting bases already listed if it wanted to
- allowing multiple items to be returned provides a way to programmatically combine mixins without having to define a new subclass for each combination
Cheers, Nick.
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