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[Python-Dev] PEP 544: Protocols - second round

Mark Shannon mark at hotpy.org
Thu May 25 13:49:33 EDT 2017 
On 24/05/17 14:31, Ivan Levkivskyi wrote:
> Hi all,
>
> After collecting suggestions in the previous discussion on python-dev
> https://mail.python.org/pipermail/python-dev/2017-March/thread.html#147629
> and playing with implementation, here is an updated version of PEP 544.
>
> --
> Ivan

I really like this PEP in general. I think this brings the type system 
for type-hints closer to Python semantics.

But there are a few points I disagree with.
I don't think Protocol types should be tied to ABCs. It just makes 
things more complex with no obvious benefit.
I also think all references to 'isinstance' and 'issubclass' should be 
removed. Type-hints should not have runtime semantics, beyond those that 
they have as classes. In fact, there is no need for protocol types to be 
classes at all.

Cheers,
Mark.
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