[Python-3000] iostack and Oh Oh (original) (raw)

tomer filiba tomerfiliba at gmail.com
Fri Dec 1 18:08:20 CET 2006

[Bill]

I agree. For instance, the [k] operation may be implemented by the Container interface generic implementation, in which case your type might have to have the Container interface

i would still like to understand how object proxying (e.g., weakrefs, RPyC), could work when all/most frameworks/libraries would be based on ABCs.

again, the problem is, your proxy is an instance of ProxyType, that refers to another, "concrete" object (e.g., getattr on the proxy performs a getattr on the concrete object). but this only works with duck typing.

the concrete object may implement certain interfaces that ProxyType does not/cannot implement (a la 3rd party). so despite the fact that the proxy object behaves just like the concrete object, they are of different types and ABCs. checking if the proxy implements an interface may fail, although the proxy is sufficient for whatever purposes you wished to use it.

the only way out of this, that i can think of, would require introducing a does_implement special method that will be called by does_implement(), or whatever the name will be. of course you could add a new ABC for that purpose, i.e., CustomImplementer.

that way, ProxyType will derive from CustomImplementer, and could perform all the necessary magic inside, to look like the concrete object.

if custom proxies couldn't override the default implementation checking mechanism (such as isinstance), i'm strongly against that.

-tomer

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