Removing None objects from a sequence

[MRAB]

Kirk Strauser wrote:
> At 2008-12-12T15:51:15Z, Marco Mariani <marco at sferacarta.com> writes:
> 
>> Filip Gruszczyński wrote:
>>
>>> I am not doing it, because I need it. I can as well use "if not elem
>>> is None",
> 
>> I suggest "if elem is not None", which is not quite the same.
> 
> So what's the difference exactly?  "foo is not None" is actually surprising
> to me, since "not None" is True.  "0 is True" is False, but "0 is not None"
> is True.  Why is that?
 >
I suppose that it should really be "not is" (cp "not in"), but Guido 
chose to follow the English pattern "is not". "not" returns a Boolean 
(or originally an int) and "is" checks for identity, but the result of 
"is False" or "is True" is down to implementation details in the 
interpreter, so you wouldn't write "is not ..." to mean "is (not ...)" 
anyway, and in practice it's not a problem.