[Python-ideas] the error that raises an AttributeError should be passed to __getattr__

[Jason Maldonis]

Hi everyone,

A while back I had a conversation with some folks over on python-list. I
was having issues implementing error handling of `AttributeError`s using
`__getattr__`.

My problem is that it is currently impossible for a `__getattr__` in Python
to know which method raised the `AttributeError` that was caught by
`__getattr__` if there are nested methods.

For example, we cannot tell the difference between `A.x` not existing
(which would raise an AttributeError) and some attribute inside `A.x` not
existing (which also raises an AttributeError).  This is evident from the
stack trace that gets printed to screen, but `__getattr__` doesn't get that
stack trace.

I propose that the error that triggers an `AttributeError` should get
passed to `__getattr__` (if `__getattr__` exists of course).  Then, when
handling errors, users could dig into the problematic error if they so
desire.

What do you think?

Best,
Jason
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.python.org/pipermail/python-ideas/attachments/20170619/d7767f65/attachment.html>