On 11/30/2017 7:22 PM, Eric V. Smith wrote:
On 11/30/2017 1:30 PM, Brett Cannon wrote:
On Thu, 30 Nov 2017 at 05:00 Eric V. Smith <e...@trueblade.com
<mailto:e...@trueblade.com>> wrote:
On 11/30/2017 6:59 AM, Antoine Pitrou wrote:
>
> Or, simply, is_dataclass_instance(), which is even longer, but
far more
> readable thanks to explicit word boundaries :-)
That actually doesn't bother me. I think this API will be used
rarely,
if ever. Or more realistically, it should be used rarely: what
actually
happens will no doubt surprise me.
So I'm okay with is_dataclass_instance() and is_dataclass_class().
But then I'm also okay with dropping the API entirely. nametuple has
lived for years without it, although Raymond's advice there is
that if
you really want to know, look for _fields. See
https://bugs.python.org/issue7796#msg99869 and the following
discussion.
My question was going to be whether this is even necessary. :) Perhaps
we just drop it for now and add it in if we find there's a public need
for it?
That's what I'm leaning toward. I've been trying to figure out what
attr.has() or hasattr(obj, '_fields') are actually used for. The attrs
version is hard to search for, and while I see the question about
namedtuples asked fairly often on SO, I haven't seen an actual use case.
It's easy enough for someone to write their own isdataclass(),
admittedly using an undocumented feature.
Actually there's a supported way to write your own isdataclass(): call
dataclasses.fields(obj). If it throws a TypeError, it's not a dataclass
instance or class. I'll add a note to the PEP.
Eric.
So I'm thinking let's drop it and then gauge the demand for it, if any.
Eric.
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