[Python-Dev] PEP 544: Protocols

[Matthias Kramm]

I'm a big fan of this. I really want structural subtyping for
http://github.com/google/pytype.

On Mon, Mar 20, 2017 at 5:00 AM, Ivan Levkivskyi <levkivskyi at gmail.com>
wrote:

> Explicitly declaring implementation
> -----------------------------------
>
> To explicitly declare that a certain class implements the given protocols,
>

Why is this necessary? The whole point of ducktyping is that you *don't*
have to declare what you implement.

I get that it looks convenient to have your protocol A also supply some of
the methods you'd expect classes of type A to have. But completing an
implementation in that way should be done explicitly (via including a
utility class or using a decorator like functools.total_ordering), not as
side-effect of an (unnecessary) protocol declaration.
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