"x == None" vs "x is None"

[Ulli Horlacher]

Chris Angelico <rosuav at gmail.com> wrote:
> On Sun, Jan 17, 2016 at 8:51 PM, Ulli Horlacher
> <framstag at rus.uni-stuttgart.de> wrote:
> > I have seen at several places "x == None" and "x is None" within
> > if-statements.
> > What is the difference?
> > Which term should I prefer and why?
> 
> tl;dr: Prefer "x is None" as a check.

And for the negation?
"if not x is None" or "if x is not None"

I have seen the last one several times, but i do not understand it, because:

>>> x=0
>>> x is not None
True
>>> not None
True
>>> x is True
False


-- 
Ullrich Horlacher              Server und Virtualisierung
Rechenzentrum IZUS/TIK         E-Mail: horlacher at tik.uni-stuttgart.de
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