easy question on parsing python: "is not None"

[Roald de Vries]

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