[Python-Dev] Second post: PEP 557, Data Classes

Greg Ewing greg.ewing at canterbury.ac.nz
Mon Nov 27 00:04:45 EST 2017


Nick Coghlan wrote:
> Perhaps the check could be:
> 
>   (type(lhs) == type(rhs) or fields(lhs) == fields(rhs)) and all
> (individual fields match)

I think the types should *always* have to match, or at least
one should be a subclass of the other. Consider:

@dataclass
class Point3d:
     x: float
     y: float
     z: float

@dataclass
class Vector3d:
     x: float
     y: float
     z: float

Points and vectors are different things, and they should never
compare equal, even if they have the same field names and values.

-- 
Greg


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