[Python-Dev] is typing optional in dataclasses?

[MRAB]

On 2017-12-22 00:19, Gregory P. Smith wrote:
> (subject for this sub-thread updated)
>
> On Thu, Dec 21, 2017 at 4:08 PM Chris Barker <chris.barker at noaa.gov 
> <mailto:chris.barker at noaa.gov>> wrote:
>
>     On Thu, Dec 21, 2017 at 3:36 PM, Gregory P. Smith <greg at krypto.org
>     <mailto:greg at krypto.org>> wrote:
>
>          But we already have ... which does - so I'd suggest that for
>         people who are averse to importing anything from typing and
>         using the also quite readable Any.  (ie: document this as the
>         expected practice with both having the same meaning)
>
>
>     I don't think they do, actually - I haven't been following the
>     typing discussions, but someone in this thread said that ... means
>     "use the type of teh default" or something like that.
>
>
> indeed, they may not.  though if that is the definition is it 
> reasonable to say that type analyzers recognize the potential 
> recursive meaning when the _default_ is ... and treat that as Any?
>
> another option that crossed my mind was "a: 10" without using =.  but 
> that really abuses __attributes__ by sticking the default value in 
> there which the @dataclass decorator would presumably immediately need 
> to undo and fix up before returning the class.  but I don't find 
> assigning a value without an = sign to be pythonic so please lets not 
> do that! :)
>
If you allowed "a: 10" (an int value), then you might also allow "a: 
'foo'" (a string value), but wouldn't that be interpreted as a type 
called "foo"?

If you can't have a string value, then you shouldn't have an int value 
either.

[snip]