Comment by oivey

Go is a terrible point of comparison. Python’s type system should not pointlessly match what other languages have chosen due to some myopic dogma.

Python is a dynamic language where one of its major features is structural subtyping, aka duck typing. It’s effectively an alternative to inheritance. Features have been added to help support this, like TypedDicts and Protocols already. They don’t go far enough.

I want to be able to say “this function argument is a dictionary that has at least the keys a, b, and c.” It gives the contract that the function only accesses those keys, and others will be ignored. The type checker can check that the function doesn’t access undeclared keys and the annotation helps communicate to client code what the interface is supposed to be.

Lots of Python’s bolted on type checking seems to be straight jacketed to match what’s in C, Java, Go, etc. Those languages don’t contain the only possible type systems or static checkers. There’s a serious lack of imagination. Python’s type system should be designed around enabling and making safer what the language is already good at.