Ivan Ivanyuk wrote: > On Thu, 18 Jun 2020 at 11:26, Peter Otten <__pete...@web.de> wrote: >> >> Ivan Ivanyuk wrote: >> >> > Hello All, >> > >> > I have some trouble using @dataclass together with @property decorator >> > or property() function. >> > >> > From the documentation and PEP is seems that the intended behaviour of >> > @dataclass is to be the same as normal __init__() that sets instance >> > variables. >> > >> > But it seems that when using @property decorator some parts work >> > differently when relying on default values. I'm using Pyhton 3.8.3 for >> > this. >> > >> > Using the code: >> > >> > from dataclasses import dataclass >> > >> > @dataclass >> > class Container: >> > x: int = 30 >> > >> > @property >> > def x(self) -> int: >> > return self._x >> > >> > @x.setter >> > def x(self, z: int): >> > if z > 1: >> > self._x = z >> > else: >> > raise ValueError
[...] >> Your class definition is basically >> >> class Container: >> x = default_value >> x = property_x >> >> i. e. you use the same name twice. A possible workaround might be to >> define the property in a subclass. That way you get distinct namespaces >> for the default value and the property: [...] > Didn't think about it in such a way! But now that it was pointed, I > see no obvious way to resolve this in dataclass decorator given the > way it's implemented now. And while adding another class looks easy it > somewhat detracts from the dataclasses' purpose of removing > boilerplate. > > Does it seems like a good idea to ask for documenting that behaviour > in dataclasses documentation or it's not popular enough use case? I don't know. From what I've seen runtime value checking has not even been considered even though it is part of attrs which seems to be a source of inspiration for dataclasses. https://www.attrs.org/en/stable/examples.html#validators If you make a feature request on python-ideas or the bugtracker you may at least find out why this part was not copied. -- https://mail.python.org/mailman/listinfo/python-list
