On 6/19/19 8:56 AM, Franklin? Lee wrote:

For example,
    if (A <: B or A <: C) and A <: D:

This expression makes makes very clear the high-level logic being used to determine the relationships between A, B, C, and D that is being checked, and I just need to lookup what <: means to understand the nature of the comparisons.

is not much better than
    if issubclass(A, (B, C)) and issubclass(A, D):

This expression makes it very clear that a class hierarchy relationship is being checked, but I still need to reach for the reference manual to understand the semantics of a tuple being passed as an argument to issubclass(). It is not at all intuitive that

issubclass(A, (B, C))

means "Is A a subclass of B or a subclass of C?" when it could also mean "Is A a subclass of both B and C?".

especially if you don't know what either of those mean. You can search
for issubclass, but you can't search for <:.

I generally find Google searches to be useless for most operators and keywords in any language when you are looking for reference information. It is generally faster to search for online reference docs for the language and head straight to the index page. Now, whether people remember how to use indexes in the age of "search for everything" is another discussion altogether.

To show that you really do need the feature, you need to show the
complex expressions you write with issubclass that would be improved
by using an operator.

I agree, but as I pointed out above, it doesn't have to be very complex. I think a real-world example written both ways would be very helpful to the discussion.

-- 
-----------------------------------------
From there to here, from here to there,
funny things are everywhere.
           -- Theodore Geisel