[Python-Dev] Is static typing still optional? (original) (raw)

Chris Barker chris.barker at noaa.gov
Thu Dec 21 17:45:48 EST 2017

On Thu, Dec 21, 2017 at 11:55 AM, Terry Reedy <tjreedy at udel.edu> wrote:

I think the understanding problem with this feature arises from two

factors: using annotations to define possibly un-initialized slots is non-obvious; a new use of annotations for something other than static typing is a bit of a reversal of the recent pronouncement 'annotations should only be used for static typing'.

you know, that may be where part of my confusion came from -- all the talk lately has been about "type hints" and "type annotations" -- the idea of "arbitrary annotations" has been lost.

Therefore, getting the permanent doc 'right' is important.

yup.

@dataclass class C: x y = 0

I think the doc should explicitly say that uninitialized fields require annotation with something (anything, not necessarily a type) simply to avoid NameError during class creation.

would this be possible?

@dataclass class C: x: y: = 0

That is -- the colon indicates an annotation, but in this case, it's a "nothing" annotation.

It's a syntax error now, but would it be possible to change that? Or would the parsing be ambiguous? particularly in other contexts.

of course, then we'd need something to store in as a "nothing" annotation -- empty string? None? (but None might mean something) create yet anther type for "nothing_annotation"

Hmm, I may have talked myself out of it....

-CHB

--

Christopher Barker, Ph.D. Oceanographer

Emergency Response Division NOAA/NOS/OR&R (206) 526-6959 voice 7600 Sand Point Way NE (206) 526-6329 fax Seattle, WA 98115 (206) 526-6317 main reception

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