"not x in" vs. "x not in"

[Phil Martel]

Joshua Marshall <jmarshal at mathworks.com> wrote in message
news:9ag5mp$gm2$1 at news.mathworks.com...
> Rainer Deyke <root at rainerdeyke.com> wrote:
>
> > To me, 'a is not b' is confusing.  It reads like 'a is (not b)', but
acts
> > like 'not (a is b)'.  When I want to check for non-identity, I always
use
> > the form 'not (a is b)'.
>
> I suggest a new operator:
>
>   a ain't b

ain't ain't good Python... ;-)