[Steve Dower <steve.dower@python.org>]

... 

* The "``None``-aware attribute access" operator ``?.`` evaluates the
complete expression if the left hand side evaluates to a value that is not
``None``

And if the LHS does evaluate to `None` ...?  I'll assume the result is also `None` then.
 

...

 From ``inspect.py``::

     for base in object.__bases__:
         for name in getattr(base, "__abstractmethods__", ()):
             value = getattr(object, name, None)
             if getattr(value, "__isabstractmethod__", False):
                 return True

After updating to use the ``?.`` operator (and deliberately not
converting to use ``any()``)::

     for base in object.__bases__:
         for name in base?.__abstractmethods__ ?? ():
             if object?.name?.__isabstractmethod__:
                 return True

 
I got lost on the `for` here.  The part following `in`:

    for name in getattr(base, "__abstractmethods__", ()):

looks in `base` (regardless of whether `base` is `None`) for an attribute named "_abstractmethods__"..  If such an attribute exists, the value of the attribute is returned (`None` or not).  Else an AttributeError is swallowed and `()` is returned.  It's hard to see how

         for name in base?.__abstractmethods__ ?? ():

does the same.  If `base` itself is `None`, I guess it returns `()`, or if  `base` has an "_abstractmethods__" attribute then the value of that attribute is returned - unless its value is None, in which case `()` is again returned.  But if `base` is not `None` and the attribute does not exist, doesn't this raise AttributeError?  The later "Exception-aware operators" section seemed to explicitly reject the idea that `?.` and `?[]` would suppress AttributeError and/or TypeError.

In short, the original getattr() didn't care at all whether `base` was `None`, or whether the value of its "__abstractmethods__" attribute was `None`, but cared a whole lot about whether that attribute exists.  I just can't see how the updated code matches that in any of those respects.

Ignoring that and pressing on, I suffer the same kind of confusions on the `if` part.  What am I missing?  For example, do these operators swallow exceptions after all?

_______________________________________________
Python-ideas mailing list
Python-ideas@python.org
https://mail.python.org/mailman/listinfo/python-ideas
Code of Conduct: http://python.org/psf/codeofconduct/