[qewrffewqwfqew]

I find `not in` highly dubious - it makes the expression grammar awkward and harder to parse. Is `not in` a two-token operator? Or is `not` an adverb in this context? What else resembles this?

To cite an alternatice, in Tcl, `in` is an operator and its negation is `ni`. A cute pun and echo of Monty Python that I'm disappointed Python didn't follow :).

[Someone]

You should be happy, as Python 3 would have renamed it to "Ekke Ekke Ekke Ekke Ptang Zoo Boing!"

As to the "what else resembles this"? I would turn it around and ask what else could resemble this. I'm not sure the conclusion would be that "not in" is a good thing, but not sure of the reverse, either:

  if x not = 3

looks weird, but I think I could grow to like it.

[efaref]

Well, shell has the '-ne' operator, which is 'not equals' in a terser style.

Really '!=' is just an attempt at rendering '≠' using only ASCII characters. They're a bit like digraphs and trigraphs in C/C++, except everyone is used to them.

I wonder if Unicode is ubiquitous enough now that you could write a language where the real maths operators were used instead. What would that look like?

[yorwba]

Haskell allows unicode in operators and there appear to be packages that implement aliases for the default ASCII versions.

https://wiki.haskell.org/Unicode-symbols

[Latty]

Scala allows using unicode arrows (→) in place of their ASCII version (->), but not things like '≠'.

I'm currently using the Monoid font (https://larsenwork.com/monoid/), which uses ligatures to achieve the visual effect of things like the not equals symbol, while the underlying code remains the same. It's a pretty nice work-around for current languages.

[ben-schaaf]

Another alternative is the way D does it. Its the same idea as `not in` but instead of adding a 2 keyword operator and non-standard usage of negation (`not` instead of `!`) it is simply: `!in`