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Comment by tdeck | Hacker News Reader

I like Python a lot, and have been using it for personal projects since about 2010. It was only once I started working and encountering long-lived unfamiliar Python codebases regularly that I understood the benefits of type hints. It's not fun to have to trace through 5 or 6 different functions to try to figure out what type is being passed in or returned from something. It's even less fun to find out that someone made a mistake and it's actually two different incompatible things depending on the execution path.

That era of Python codebases were miserable to work in, and often ended up in the poorly though out "we don't know how this works and it has too many bugs, let's just rewrite it" category.

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> It's not fun to have to trace through 5 or 6 different functions to try to figure out what type is being passed in or returned from something.

My position is that what is intended must be made clear between type hints and the docstring. Skipping this makes for difficult to read code and has no place in a professional setting in any non-trivial codebase.

This doesn't require type hints to achieve. :param and :rtype in the docstring are fine if type hints aren't present, or for complex cases, plain English in the docstring is usually better.

:param and :rtype are type hints, just type hints that cannot be validated by tooling and are guaranteed to go out of sync with the code eventually.

Proper type hints are typically very easy to add if the codebase is not a mess that passes things around far and wide with no validation. If it is, the problem is not with the type hints.

I agree, although I've found that correct and comprehensive use of the doctoring for this purpose has not existed in the environments I've worked in, or the open source codebases I have needed to understand. Something about type hinting makes people more likely to do it.

I am sorry, but whats wrong with doing something like, `print(type(var)); exit()` and just running it once instead of digging through 5-6 stack frames?

Sometimes a function's input or return type can vary depending on the execution path? Also, inserting print statements is often not practical when working on web backend software which is kind of a big thing nowadays. If you can run the service locally, which is not a given, dependencies get mocked out and there's no guarantee that your code path will execute or that the data flowing through it will be representative.

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