[Python-Dev] PEP 443 - Single-dispatch generic functions (including ABC support) (original) (raw)

Łukasz Langa lukasz at langa.pl
Mon May 27 14:57:55 CEST 2013

On 26 maj 2013, at 01:07, PJ Eby <pje at telecommunity.com> wrote:

The PEP uses the term "implementation", and I think that actually makes a lot of sense: a generic function is composed of functions that implement the same operation for different types.

All suggested changes applied. There are still a couple of mentions of "overloads" and "overloading" in the PEP but they are unambiguous now and always refer to the general mechanism.

Last, but not least, there should be a stacking example somewhere in the doc, as in the PEP

I swapped the old examples from the docs and reused the PEP API docs in their entirety. This way it's easier to keep things consistent.

(It may also be useful to note somewhere that, due to caching, changing the base classes of an existing class may not change what implementation is selected the next time the generic function is invoked with an argument of that type or a subclass thereof.)

I don't think it's necessary. Abstract base classes present the same behaviour and this isn't documented anywhere:

from abc import ABC class FirstABC(ABC): pass class SecondABC(ABC): pass class ImplementsFirst(FirstABC): pass assert FirstABC in ImplementsFirst.mro assert issubclass(ImplementsFirst, FirstABC)

If we change bases of the class, it no longer reports the first in the MRO:

ImplementsFirst.bases = (SecondABC,) assert FirstABC not in ImplementsFirst.mro assert SecondABC in ImplementsFirst.mro assert issubclass(ImplementsFirst, SecondABC)

But it still reports being a subclass:

assert issubclass(ImplementsFirst, FirstABC), "sic!"

-- Best regards, Łukasz Langa

WWW: http://lukasz.langa.pl/ Twitter: @llanga IRC: ambv on #python-dev

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