The terminology I used was correct. Python has optional typing. What you are thinking of is gradual typing which Python lacks. See "Is Sound Gradual Typing Dead?" for a description on what the differences are.
If you pass a string-typed var to a func with an int-typed parameter, it will not fail at runtime. `python the_file.py` will not even emit a warning, much less a failure, because there's absolutely no runtime difference between "has types" and "does not".
That's not optional typing. It's just a standardized magic comment (which the reference implementation ignores). It's far from useless, but it's not adding typing to the language.
That appears to be a doc about Racket, which it implies does have run-time checks, from the third sentence here:
>In particular, Typed Racket’s run-time system remains largely untyped. As a result, even the completely typed configurations of our benchmarks usually import constants, functions, and classes from an untyped module in the run-time system. When these values cross this boundary at run-time, the contract system performs checks, and that imposes additional costs.
But I haven't read the whole thing. It doesn't appear to be very related - it seems to be about gradual typing in a language that does run-time checks (with ways to disable them for performance purposes).
Typed python has no additional checks than untyped. So it's still untyped. You wouldn't claim my "// int" comments add optional typing to JavaScript, would you?
>Note: The Python runtime does not enforce function and variable type annotations. They can be used by third party tools such as type checkers, IDEs, linters, etc.
It's not a doc about Racket, it's a conference paper. Had you read it you would have found "Optional typing can be traced as far back as MACLISP, which allowed users to declare (unchecked) type specifications [15, §14.2] in an otherwise untyped language." and "Contemporary optional type systems have been developed for Clojure [8], Lua [14], Python, [10]," where the footnote references MyPy. Type hinting is the mechanism through which optional typing is implemented.
MACLISP I can't really comment on as I don't know it and Wikipedia makes no mention of this, but yeah - MyPy is definitely an optionally-typed python code checker. It fits that category for both comment-based and in-language type hints, because it performs checks based on that info.
For Python itself though: if you have a syntactic element which does not change behavior in literally any way, whether present or absent and regardless of what it contains: sounds like a comment to me.
