I am working on a PR for typeshed that will use a protocol (_SupportsLessThan) to make sure that the parameterized type of arguments to `sorted` can be sorted—which requires they implement `__lt__`. In Python 3, there are two cases relevant to this discussion: - if no `key` argument is given, then the first arg of `sorted` must be `Iterable[SupportsLessThan]`. - if a `key` argument is given, then the first argument can be `Iterable[Any]`, but the `key` argument must be a callable that returns a value that `SupportsLessThan` The same PR is supposed to enhance the type hints for the `list.sort` method, but in this case, I don't know how to deal with the case where no `key` is given. Can I just annotate `self`? class list: ... def sort(self: List[SupportsLessThan]... etc.... The whole thing is more complicated than I just described, @overload is required to make the `sorted` annotations. My question is about constraining `self`, because it turns out that not all list instances are sortable... Cheers, Luciano -- Luciano Ramalho | Author of Fluent Python (O'Reilly, 2015) | http://shop.oreilly.com/product/0636920032519.do | Technical Principal at ThoughtWorks | Twitter: @ramalhoorg
El lun., 1 jun. 2020 a las 13:46, Luciano Ramalho (<luciano@ramalho.org>) escribió:
I am working on a PR for typeshed that will use a protocol (_SupportsLessThan) to make sure that the parameterized type of arguments to `sorted` can be sorted—which requires they implement `__lt__`.
In Python 3, there are two cases relevant to this discussion:
- if no `key` argument is given, then the first arg of `sorted` must be `Iterable[SupportsLessThan]`. - if a `key` argument is given, then the first argument can be `Iterable[Any]`, but the `key` argument must be a callable that returns a value that `SupportsLessThan`
The same PR is supposed to enhance the type hints for the `list.sort` method, but in this case, I don't know how to deal with the case where no `key` is given. Can I just annotate `self`?
I believe that should be OK. See mypy's documentation at https://mypy.readthedocs.io/en/stable/more_types.html#advanced-uses-of-self-.... I don't know whether other typecheckers fully support this pattern (pyanalyze certainly doesn't), but it should be acceptable in tyeshed.
class list: ... def sort(self: List[SupportsLessThan]... etc....
The whole thing is more complicated than I just described, @overload is required to make the `sorted` annotations. My question is about constraining `self`, because it turns out that not all list instances are sortable...
Cheers,
Luciano
-- Luciano Ramalho | Author of Fluent Python (O'Reilly, 2015) | http://shop.oreilly.com/product/0636920032519.do | Technical Principal at ThoughtWorks | Twitter: @ramalhoorg _______________________________________________ Typing-sig mailing list -- typing-sig@python.org To unsubscribe send an email to typing-sig-leave@python.org https://mail.python.org/mailman3/lists/typing-sig.python.org/ Member address: jelle.zijlstra@gmail.com
Thank you, Jelle! Cheers, Luciano On Mon, Jun 1, 2020 at 5:57 PM Jelle Zijlstra <jelle.zijlstra@gmail.com> wrote:
El lun., 1 jun. 2020 a las 13:46, Luciano Ramalho (<luciano@ramalho.org>) escribió:
I am working on a PR for typeshed that will use a protocol (_SupportsLessThan) to make sure that the parameterized type of arguments to `sorted` can be sorted—which requires they implement `__lt__`.
In Python 3, there are two cases relevant to this discussion:
- if no `key` argument is given, then the first arg of `sorted` must be `Iterable[SupportsLessThan]`. - if a `key` argument is given, then the first argument can be `Iterable[Any]`, but the `key` argument must be a callable that returns a value that `SupportsLessThan`
The same PR is supposed to enhance the type hints for the `list.sort` method, but in this case, I don't know how to deal with the case where no `key` is given. Can I just annotate `self`?
I believe that should be OK. See mypy's documentation at https://mypy.readthedocs.io/en/stable/more_types.html#advanced-uses-of-self-.... I don't know whether other typecheckers fully support this pattern (pyanalyze certainly doesn't), but it should be acceptable in tyeshed.
class list: ... def sort(self: List[SupportsLessThan]... etc....
The whole thing is more complicated than I just described, @overload is required to make the `sorted` annotations. My question is about constraining `self`, because it turns out that not all list instances are sortable...
Cheers,
Luciano
-- Luciano Ramalho | Author of Fluent Python (O'Reilly, 2015) | http://shop.oreilly.com/product/0636920032519.do | Technical Principal at ThoughtWorks | Twitter: @ramalhoorg _______________________________________________ Typing-sig mailing list -- typing-sig@python.org To unsubscribe send an email to typing-sig-leave@python.org https://mail.python.org/mailman3/lists/typing-sig.python.org/ Member address: jelle.zijlstra@gmail.com
-- Luciano Ramalho | Author of Fluent Python (O'Reilly, 2015) | http://shop.oreilly.com/product/0636920032519.do | Technical Principal at ThoughtWorks | Twitter: @ramalhoorg
participants (3)
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Jelle Zijlstra -
Luciano Ramalho -
Mark Mendoza