Finished creating 2 issues on the meanwhile:
bpo-39264 to fix UserDict.get().
bpo-39267 to fix dict.__missing__ & dict.get() documentation.
Both include a PR.
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>
> [Bar Harel]
> > As for get(). Current implementation of UserDict returns the default
> value
> > for get() if __missing__() raises KeyError. Which sounds reasonable to
> me.
> > After all, you would logically expect __missing__ to be called for get()
> > as you tried to get a non-existing valu
On Wed, Jan 8, 2020 at 12:02 PM Ethan Furman wrote:
> I disagree. My understanding of the purpose behind get() is to get a value
> or return the default specified in the get() call, not to create a new key
> (which the default __missing__ does).
>
Right. For comparison, defaultdict.get() doesn'
[Bar Harel]:
I was just about to fix dict's get() to call __missing__ if a key doesn't
exist (before returning the default value) but realized that although small,
that patch can cause future issues. Right now there's an inconsistency:
The reason for this inconsistency is because the Mapping ab
Sounds good to me.
If you want a second opinion als Raymond Hettinger.
On Wed, Jan 8, 2020 at 11:09 Bar Harel wrote:
> Well it depends on the consensus for __missing__, and the consensus for
> get().
>
> I believe modifying get() is out of the question as it will lead to
> breakage. If so, whet
Well it depends on the consensus for __missing__, and the consensus for
get().
I believe modifying get() is out of the question as it will lead to
breakage. If so, whether it's a quirk or not doesn't matter as we can't
change it. Adding a comment to the docs should suffice, along with updating
the
Hum, it looks like the UserDict.get() behavior is an accident due to the
way Mapping.get() is implemented. The comment there says
'D.get(k[,d]) -> D[k] if k in D, else d. d defaults to None.'
but the implementation just tries D[k] and catches KeyError. The
UserDict.__contains__() implementat
Sorry for the double post then :-)
As for get(). Current implementation of UserDict returns the default value
for get() if __missing__() raises KeyError. Which sounds reasonable to me.
After all, you would logically expect __missing__ to be called for get() as
you tried to get a non-existing value
(Note: We received your email twice.)
I don't think __missing__ should be called by get() -- get() already has a
way to deal with missing keys, and making it use two different mechanisms
would be weird (e.g. if get() calls __missing__, is the default value ever
used?).
To answer your second quest
