easy question on parsing python: "is not None"

[Dave Angel]

Roald de Vries wrote:
> <div class="moz-text-flowed" style="font-family: -moz-fixed">On Aug 5, 
> 2010, at 5:42 PM, wheres pythonmonks wrote:
>> How does "x is not None" make any sense?  "not x is None" does make 
>> sense.
>>
>> I can only surmise that in this context (preceding is) "not" is not a
>> unary right-associative operator, therefore:
>>
>> x is not None === IS_NOTEQ(X, None)
>>
>> Beside "not in" which seems to work similarly, is there other
>> syntactical sugar like this that I should be aware of?
>
> 'not None' first casts None to a bool, and then applies 'not', so 'x 
> is not None' means 'x is True'.
> 'not x is None' is the same as 'not (x is None)'
>
> Cheers, Roald
>
Did you try it?

Python 2.6.4 (r264:75706, Jan 22 2010, 16:41:54) [MSC v.1500 32 bit
win32
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 >>> 4 is not None
True
 >>> True is not None
True
 >>> False is not None
True
 >>> None is not None
False
 >>>

Looks to me like
   x is not None

is equivalent to
   not (x is None)

(I get same results for 3.1)

DaveA