Are Python and mypy smart enough to know the data types being assigned on lines 8 and 9? Even without the type hint, won’t mypy still complain if I later try to assign 1 to self.letter or “A” to self.freq?

I think you are being rhetoric here 😅 but I thought I should add my two cents but tbh I would like to know the answer as well 😂 From my limited knowledge of using python, Mypy would still complain but I think the main use of type hints that I have found is when language servers used in IDE's help the programmer to look at the function signature/definition and not make any mistakes. For example, when you're writing something in VSCode and use a package it gives you an autocomplete suggestion which also contains the information for the type expected in a particular argument. This immediately makes the programmer aware that they are making a mistake because language servers raise a warning squiggly lines whereas the type hint inside the def doesn't (I think). If I'm wrong, let me know as well 😂 I would also like to know whether language servers would be able raise a flag when type hint is only provided in the definition and not the signature of the function.

You and I agree with each other. The most helpful use of type hints is in function parameters and return types.

Does this change run counter to flake8 return error R504? https://github.com/afonasev/flake8-return#errors