Am Mittwoch, 13. Januar 2016 21:57:00 UTC+1 schrieb John H Palmieri:
>
>
>
> On Wednesday, January 13, 2016 at 12:43:25 PM UTC-8, Martin R wrote:
>>
>> To understand the difference between ‘is’ and ‘==‘ may require some
>>> background in programming.
>>>
>>> Specifically, “a==b” evaluates to “True” if the objects ‘a’ and ‘b’
>>> “evaluate to the same *value*”, while “a is b” evaluates to “True” if the
>>> objects ‘a’ and ‘b’ *are the same” (i.e., are located at the same locations
>>> in RAM).
>>>
>>> Yes, I understand this. (and to make sure, I checked the python doc)
>>
>> To answer your questions, your impression is not correct (but you are not
>>> alone), and the code is not misleading (making the rash assumption that it
>>> is correct, which I have not verified).
>>>
>>> Now I do not understand. FormalSums inherits from UniqueRepresentation.
>>
>
> "FormalSums" inherits from UniqueRepresentation. "FormalSum" does not, as
> far as I can tell. So for instances of FormalSum, which are what arise in
> the snippet you posted, "==" may not be the same as "is".
>
> Now I am entirely confused. I read:
if isinstance(x, FormalSum):
P = x.parent()
I would think that P is now an instance of "FormalSums", not an instance of
"FormalSum"?
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