Usefulness of the "not in" operator

[Stefaan Himpe]

>
> So what is the usefulness of the "not in" operator ? Recall what Zen of
> Python tells
>
> There should be one-- and preferably only one --obvious way to do it.

the zen of python also says (amongst other things):

...
Readability counts.
...
Although practicality beats purity
...

Best regards,
Stefaan.