Are dicts supposed to raise comparison errors

[Robin Becker]

On 01/08/2018 09:52, Chris Angelico wrote:
> On Wed, Aug 1, 2018 at 6:36 PM, Robin Becker <robin at reportlab.com> wrote:
>> On 31/07/2018 16:52, Chris Angelico wrote:
>..........
>>
>> it says explicitly that numeric keys will use numeric comparison, but no
.........
>>
> 
> Technically, the comparison used is:
> 
> a is b or a == b
> 
> in other words, identity will match, but mainly, equality is used. The
> identity check improves performance in many common cases, and also
> avoids pathological cases involving float("nan"), but in general
> discussion, it's assumed that value rather than identity is the
> comparison used.
> 
> ChrisA
> 

If the testing were done in that order then no comparison warning would occur as inspection shows 'a' is not b'a'

  > C:\code\hg-repos\reportlab\tmp>\python37\python.exe -b -Wall
> Python 3.7.0 (v3.7.0:1bf9cc5093, Jun 27 2018, 04:59:51) [MSC v.1914 64 bit (AMD64)] on win32
> Type "help", "copyright", "credits" or "license" for more information.
>>>> 'a' is b'a'
> False
>>>>

so presumably the testing goes something like

a is b or (a==b if comparable(a,b) else False)

even so I still think errors/warnings created internally by implementers should not be exposed. It's not a big deal. I'm a bit 
surprised that we don't have a mapping which uses only identity as that would be faster.
-- 
Robin Becker