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Small but important correction required in point 3 of the TL;DR: > Python doesn’t care about types at runtime This should say "Python doesn't care about type

Small but important correction required in point 3 of the TL;DR: > Python doesn’t care about types at runtime This should say "Python doesn't care about type annotations at runtime." Python _does_ care about types at runtime - but it doesn't use type annotations to compute them. That doesn't detract from what's otherwise a really clear and helpful post. Python is living through a schizophrenic period in its evolution, and it's causing some problems. I hope it gets ironed out, though don't underestimate the difficulty. Python remains my go-to for many problems: a joy to use (for me) in many cases. But I definitely feel the need for static typing as codebase size increases. Having type annotations is good, but not being able to rely on them (i.e. static typing is not sound) adds to cognitive load and detracts from a confident development experience.

the_af 3y ago
I agree with the gist of your comment. I will add that, in my experience, having type annotations that are unreliable, cumbersome, with so many edge cases and requiring this kind of magic (e.g. "if TYPE_CHECKING", etc) which is beyond most "casual" Python users effectively means type annotations are a very hard sell for most non-hardcore team mates. I've been in a position to try improving processes and code quality of the Python codebase, and introducing mypy and type annotations has always been a very hard sell. The team just won't accept the benefits, given the difficulties in using it. If only Python made it easier and more reliable, but the current state is a mess. I come from the static typing world, so of course I see the benefits. But most/all of my team mates don't, and so they see this as some really odd hoops I want them to jump through, for minimal benefit (in their eyes).
- durumu 3y ago
  I think type annotations are extremely valuable even if you don't use mypy. On my team we basically use them as comments that are understood by the IDE, but aren't enforced. Of course comments can lie, but appeasing mypy really is a lot of work, and I would generally rather have a slightly dishonest but mostly correct type hint than some TypeVar monstrosity or, worse, Any.
  - the_af 3y ago
    Hm. Type annotations as comments is the ultimate annoyance to my coworkers. They really do see them as "what's the point" in that case. Plus, like you say, they are misleading. The look like code, but they don't do anything.
    - durumu 3y ago
      I think if you're already documenting function argument types, there is no point. But in my experience it's unworkable to ask people to write full documentation for every function, but requiring type hints is not as hard and is nearly as useful. It is a little weird that they look like code, but I think you get used to it.

the_af 3y ago

I agree with the gist of your comment. I will add that, in my experience, having type annotations that are unreliable, cumbersome, with so many edge cases and requiring this kind of magic (e.g. "if TYPE_CHECKING", etc) which is beyond most "casual" Python users effectively means type annotations are a very hard sell for most non-hardcore team mates. I've been in a position to try improving processes and code quality of the Python codebase, and introducing mypy and type annotations has always been a very hard sell. The team just won't accept the benefits, given the difficulties in using it. If only Python made it easier and more reliable, but the current state is a mess. I come from the static typing world, so of course I see the benefits. But most/all of my team mates don't, and so they see this as some really odd hoops I want them to jump through, for minimal benefit (in their eyes).

durumu 3y ago
I think type annotations are extremely valuable even if you don't use mypy. On my team we basically use them as comments that are understood by the IDE, but aren't enforced. Of course comments can lie, but appeasing mypy really is a lot of work, and I would generally rather have a slightly dishonest but mostly correct type hint than some TypeVar monstrosity or, worse, Any.
- the_af 3y ago
  Hm. Type annotations as comments is the ultimate annoyance to my coworkers. They really do see them as "what's the point" in that case. Plus, like you say, they are misleading. The look like code, but they don't do anything.
  - durumu 3y ago
    I think if you're already documenting function argument types, there is no point. But in my experience it's unworkable to ask people to write full documentation for every function, but requiring type hints is not as hard and is nearly as useful. It is a little weird that they look like code, but I think you get used to it.