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On Sat, Nov 28, 2015 at 7:32 AM, 王珺 email@example.com wrote:
At first I think of adding AttributeMissError. In that case, object.__getattr__ (here self.x.__getattr__) could turn AttributeMissError to AttributeError. But after some consideration I think there's no need to add an extra Exception. Just ignore the title of that issue.
So... if I'm understanding the issue correctly, it's about the interaction of @property and __getattr__? You're talking about this as a boundary over which AttributeError changes. Borrowing your example from the tracker issue:
class property(property): def __get__(self, a): try: return super().__get__(a) except AttributeError as e: raise RuntimeError("Property raised AttributeError") from e
class A(): def __init__(self, x=None): self.x = x
@property def t(self): return self.x.t def __getattr__(self, name): return 'default'
Traceback (most recent call last): File "attrerr.py", line 4, in __get__ return super().__get__(*a) File "attrerr.py", line 14, in t return self.x.t AttributeError: 'NoneType' object has no attribute 't'
The above exception was the direct cause of the following exception:
Traceback (most recent call last): File "attrerr.py", line 19, in <module> print(A().t) File "attrerr.py", line 6, in __get__ raise RuntimeError("Property raised AttributeError") from e RuntimeError: Property raised AttributeError
This would create a boundary, same as PEP 479 does for StopIteration, across which AttributeError becomes RuntimeError.
This could be incorporated into the built-in property if desired, or kept on a per-module basis with the above.