On 12/10/2017 5:00 PM, Raymond Hettinger wrote:
On Dec 10, 2017, at 1:37 PM, Eric V. Smith <[email protected]> wrote:
On 12/10/2017 4:29 PM, Ivan Levkivskyi wrote:
On 10 December 2017 at 22:24, Raymond Hettinger
<[email protected]<mailto:[email protected]>> wrote:
Without typing (only the first currently works):
Point = namedtuple('Point', ['x', 'y', 'z']) #
underlying store is a tuple
Point = make_dataclass('Point', ['x', 'y', 'z']) #
underlying store is an instance dict
Hm, I think this is a bug in implementation. The second form should also work.
Agreed.
I have a bunch of pending changes for dataclasses. I'll add this.
Eric.
Thanks Eric and Ivan. You're both very responsive. I appreciate the enormous
efforts you're putting in to getting this right.
Thank you for your feedback. It's very helpful.
I see a couple of options:
1a: Use a default type annotation, if one is not is supplied. typing.Any
would presumably make the most sense.
1b: Use None if not type is supplied.
2: Rework the code to not require annotations at all.
I think I'd prefer 1a, since it's easy. However, typing is not currently
imported by dataclasses.py. There's an argument that it really needs to
be, and I should just bite the bullet and live with it. Possibly with
Ivan's PEP 560 work my concern on importing typing goes away.
1b would be easy, but I don't like using non-types for annotations. 2
would be okay, but then that would be the only time __annotations__
wouldn't be set on a dataclass.
I suggest two other fix-ups:
1) Let make_dataclass() pass through keyword arguments to _process_class(), so
that this will work:
Point = make_dataclass('Point', ['x', 'y', 'z'], order=True)
Agreed.
2) Change the default value for "hash" from "None" to "False". This might take
a little effort because there is currently an oddity where setting hash=False causes it to be hashable. I'm
pretty sure this wasn't intended ;-)
It's sufficiently confusing that I need to sit down when I have some
free time and noodle this through. But it's still on my radar.
Eric.
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