[Python-3000] Draft pre-PEP: function annotations (original) (raw)

Phillip J. Eby pje at telecommunity.com
Tue Aug 15 18:09:48 CEST 2006

At 06:56 AM 8/15/2006 -0700, Paul Prescod wrote:

On 8/14/06, Phillip J. Eby <<mailto:pje at telecommunity.com>pje at telecommunity.com> wrote:

At 1:51 PM 8/14/2006 -0700, "Paul Prescod" <<mailto:paul at prescod.net>paul at prescod.net> wrote: >On 8/14/06, Jim Jewett <<mailto:jimjjewett at gmail.com>jimjjewett at gmail.com> wrote: > > The definition of a type as an annotation should probably be either > > defined or explicitly undefined. Earlier discussions talked about > > things like > > > > def f (a:int, b:(float | Decimal), c:[int, str, X]) ->str) > > >I think that's a separate (large!) PEP. This PEP should disallow frameworks >from inventing their own meaning for this syntax (requiring them to at least >wrap). Then Guido and crew can dig into this issue on their own schedule.

I see we haven't made nearly as much progress on the concept of "no predefined semantics" as I thought we had. :( i.e., -1 on constraining what types mean. I don't understand what you're saying.

I'm saying that we don't need a predefined semantics for annotation objects of type 'type'; i.e. the PEP need not define what "a:int" means. I'm roughly +0 on having predefined semantics for annotation objects of type 'list' and 'str'.

1. Do you (still?) agree that the meaning of the list type should be defined as a semantically neutral container for other annotations?

I believe it should be a recommended best practice -- "defined" is too strong a word.

2. Do you (still?) agree that the meanings of ALL built-in types at the top-level should be reserved for the Python language designers and should not be randomly used by framework developers. In other words: the function type declaration syntax above should not be used by one third party type checker while another third-party type checker uses the same structure to mean something totally different. Note that I don't mind if they have conflicting semantics for the same expression as long as the end-user is forced to declare which semantic model they are using:

I don't see a reason to require an explicit wrapper except as a disambiguator. That is, until you actually need them, discriminator-wrappers are a YAGNI.

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