[Python-Dev] Not Deprecating Arbitrary Function Annotations

[Ryan Gonzalez]

PSF. Nothing personal, of course...

On October 5, 2015 3:01:11 PM CDT, Guido van Rossum <guido at python.org> wrote:
>"They"?
>
>On Mon, Oct 5, 2015 at 12:57 PM, Ryan Gonzalez <rymg19 at gmail.com>
>wrote:
>
>> There is one reason I would be really freaking mad if they deprecated
>> other uses of annotations:
>>
>> https://pypi.python.org/pypi/plac
>>
>> On October 5, 2015 1:55:37 PM CDT, Steve Wedig <stevewedig at gmail.com>
>> wrote:
>> >Congratulations on the release of 3.5 and Pep 484. I've used Python
>> >professionally for 10 years and I believe type hints will make it
>> >easier to
>> >work with large codebases evolving over time. My only concern about
>Pep
>> >484
>> >is the discussion of whether or not to deprecate arbitrary function
>> >annotations.
>> >https://www.python.org/dev/peps/pep-0484/
>> >
>> >I would like to request that arbitrary function annotations are not
>> >deprecated for three reasons:
>> >1. Backwards Compatibility
>> >2. Type Experimentation
>> >3. Embedded Languages
>> >
>> >1. Backwards Compatibility
>> >After reading Pep 3107 my team has made significant use of
>non-standard
>> >annotations. It would be a serious burden to be forced to port our
>> >annotations back to decorators. This would also make our codebase
>> >considerably less readable because function annotations are much
>more
>> >readable than input/output annotations relegated to decorators.
>> >https://www.python.org/dev/peps/pep-3107/
>> >
>> >2. Type Experimentation
>> >Arbitrary function annotations allow developers to experiment with
>> >potential type system improvements in real projects. Ideas can be
>> >validated
>> >before officially adding them to the language. This seems like an
>> >advantage
>> >that should be preserved. After all, Pep 484 says it was strongly
>> >inspired
>> >by MyPy, an existing project.
>> >http://mypy-lang.org/
>> >
>> >3. Embedded Languages
>> >Python's flexibility makes it an amazing language to embed other
>> >languages
>> >in. In this regard, Python 3's addition of arbitrary function
>> >annotations
>> >and class decorators complements Python 2's dynamic typing, function
>> >decorators, reflection, metaclasses, properties, magic methods,
>> >generators,
>> >and keyword arguments. Arbitrary function annotations are a crucial
>> >part of
>> >this toolkit, and this feature is not available in most other
>> >languages.
>> >For anyone interested in the utility and mechanics of embedded
>> >languages,
>> >I'd recommend Martin Fowler's book: Domain Specific Languages.
>> >
>>
>http://www.amazon.com/Domain-Specific-Languages-Addison-Wesley-Signature-Series/dp/0321712943
>> >
>> >So I agree with the course of action mentioned in Pep 484 that
>avoids
>> >runtime deprecation of arbitrary function annotation: "Another
>possible
>> >outcome would be that type hints will eventually become the default
>> >meaning
>> >for annotations, but that there will always remain an option to
>disable
>> >them." I would only add that there should be a way to disable type
>> >checking
>> >for an entire directory (recursively). This would be useful for
>> >codebases
>> >that have not been ported to standard annotations yet, and for
>> >codebases
>> >that will not be ported for the reasons listed above.
>> >
>> >Thanks for your consideration.
>> >
>> >Best,
>> >Steve
>> >
>> >
>>
>>------------------------------------------------------------------------
>> >
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>>
>> --
>> Sent from my Nexus 5 with K-9 Mail. Please excuse my brevity.
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>
>
>
>-- 
>--Guido van Rossum (python.org/~guido)

-- 
Sent from my Nexus 5 with K-9 Mail. Please excuse my brevity.
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