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Python has optional type hinting for optional static analysis tools (e.g. mypy). Types aren't checked at runtime.

by Groxx 6y ago

bjourne 6y ago
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.
- Groxx 6y ago
  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.
  - bjourne 6y ago
    Yes, that is "optional typing." Read the article I referenced.
    - Groxx 6y ago
      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? --- edit: here, take it from the source instead: https://docs.python.org/3/library/typing.html https://docs.python.org/3/library/typing.html Note the title is "support for type hints" and this prominent note is right at the top: >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.
      - bjourne 6y ago
        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.
        Groxx 6y ago
        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.

Python has optional type hinting for optional static analysis tools (e.g. mypy). Types aren't checked at runtime.

by Groxx 6y ago

Python has optional type hinting for optional static analysis tools (e.g. mypy). Types aren't checked at runtime.

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.

Groxx 6y ago
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.
- bjourne 6y ago
  Yes, that is "optional typing." Read the article I referenced.
  - Groxx 6y ago
    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? --- edit: here, take it from the source instead: https://docs.python.org/3/library/typing.html https://docs.python.org/3/library/typing.html Note the title is "support for type hints" and this prominent note is right at the top: >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.
    - bjourne 6y ago
      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.
      - Groxx 6y ago
        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.