`<:` kind of notation would look more clear, I agree. My proposition came after thinking the wording used in Python. issubclass() - is subclass? By definition, subclass reminds me set theory. https://en.wikipedia.org/wiki/Subclass_(set_theory) which also has a relativity with Subtyping as Guido pointed out. And, we have operator support for set() as you can see here https://docs.python.org/3/library/stdtypes.html#set `set <= other` With this logic, since Python has its own way of being practical and predictable in some ways, I would except to have an operator like `<:`, which some other languages already possess. A <: B against issubclass(A, B) looks more elegant, and purpose driven syntax like most of other types. I see that there is also `issubset` method which is equivalent to `set <= other`. Therefore I find this a little bit inconsistent that we don't apply the similar logic for issubclass. I don't know if we could achieve same performance of issubclass itself with the operator (I think we can) but even it's not the case, people who uses Python to write their scripts very fast, that would be a lovely addition.