On 28 May 2017 at 16:13, Kevin Conway <kevinjacobcon...@gmail.com> wrote:
> > Some of the possible options for the title are > It seems like you're talking about something most other languages would > refer to as "Interfaces". What is unique about this proposal that would > call for not using the industry standard language? > Well, I would say there is no "industry standard language" about structural subtyping. There are interfaces, protocols, traits, mixins, typeclasses, roles, and probably some other terms I am not aware of - all with subtly different semantics in different languages. There are several reasons why we use term protocol and not interface. Two important reasons for me are: * The term protocol is already de-facto standard in Python for things like sequence protocol, iterator protocol, descriptor protocol, etc. * Protocols are very different from Java interfaces in one important aspect: they don't require explicit declaration of implementation, they are mainly oriented on duck-typing. Maybe we need to add a short section to rejected ideas? > Type-hints should not have runtime semantics, beyond those that they have > as classes > > lots of code uses isinstance(obj, collections.abc.Iterable) and > similar checks with other ABCs > Having interfaces defined as something extended from abc doesn't > necessitate their use at runtime, but it does open up a great deal of > options for those of us who want to do so. I've been leveraging abc for a > few years now to implement a lightweight version of what this PEP is > attempting to achieve > IIUC this is not the main goal of the PEP, the main goal is to provide support/standard for _static_ structural subtyping. Possibility to use protocols in runtime context is rather a minor bonus that exists mostly to provide a seamless transition for projects that already use ABCs. -- Ivan
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