[Python-Dev] Second post: PEP 557, Data Classes
Sebastian Rittau
srittau at rittau.biz
Mon Nov 27 06:01:52 EST 2017
On 25.11.2017 22:06, Eric V. Smith wrote:
> The updated version should show up at
> https://www.python.org/dev/peps/pep-0557/ shortly.
This PEP looks very promising and will make my life quite a bit easier,
since we are using a pattern involving data classes. Currently, we write
the constructor by hand.
> The major changes from the previous version are:
>
> - Add InitVar to specify initialize-only fields.
This is the only feature that does not sit right with me. It looks very
obscure and "hacky". From what I understand, we are supposed to use the
field syntax to define constructor arguments. I'd argue that the name
"initialize-only fields" is a misnomer, which only hides the fact that
this has nothing to do with fields at all. Couldn't dataclassses just
pass *args and **kwargs to __post_init__()? Type checkers need to be
special-cases for InitVar anyway, couldn't they instead be special cased
to look at __post_init__ argument types?
- Sebastian
More information about the Python-Dev
mailing list