So this would make `a` a new keyword. I don't think that could be added into python 4 at the earliest because it would immediately break all code for which `a` is a variable name.

I can appreciate wanting to make simple operations easy to read, though I think this relies too much on understanding English and wouldn't be intuitive for people who aren't English speaking. I am native English speaking so I wouldn't know for sure, but I think accepting that "or" is the same as "||" is an easier jump to make than "x is a y" being a construct for indicating that x belongs to the y class.

If you need this English-style syntax, I believe `type(x) is y` is guaranteed to be True if x is exactly of the y type and not one of its super classes.

On Fri, May 1, 2020, 1:27 PM gbs--- via Python-ideas <python-ideas@python.org> wrote:

In cases where it makes sense to do explicit type checking (with ABCs or whatever), I really detest the look of the isinstance() function.

if isinstance(thing, Fruit) and not isinstance(thing, Apple):

Yucky.

What I really want to write is:

if thing is a Fruit and thing is not an Apple:

and after thinking about it on and off for a while I wonder if it might indeed be possible to teach the parser to handle that in a way that eliminates almost all possible ambiguity with the regular "is", including perhaps 100% of all existing standard library code and almost all user code?

Maybe this has been considered at some point in the past? The "is [not] a|an" proposal would at least be a strong contender for "hardest thing to search for on the internet" lol.

Thanks!

Gavin
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