> On Sep 11, 2017, at 4:21 PM, Yury Selivanov <yselivanov...@gmail.com> wrote: > > I'm one of those who used annotations for other purposes than type > hints. And even if annotations became strings in Python 3.7 *without > future import*, fixing my libraries would be easy -- just add an > eval(). > > That said, the PEP doesn't cover an alternative solution: > > 1. Add another special attribute to functions: __annotations_text__. > > 2. __annotations__ becomes a dynamic Mapping, which evaluates stuff > from __annotations_text__ *lazily*. > > 3. Recommend linters and IDEs to support "# pragma: annotations", as a > way to say that the Python files follows the new Python 3.7 > annotations semantics. > > That would maintain full backwards compatibility with all existing > Python libraries and would not require a future import.
I'm not very thrilled about this because lazy evaluation is subject to the new scoping rules (can't use local state) and might give a different result than before. It's not backwards compatible. A __future__ import makes it obvious that behavior is going to be different. And lazy evaluation is an unnecessary step if `get_type_hints()` is used later on so it's unnecessary for the most common usage of annotations. Finally, I don't think we ever had a "# pragma" suggestion coming from CPython. In reality, people wouldn't bother putting it in most files so tools would have to assume that forward references are correct *and* avoid raising errors about invalid names used in annotations. This is loss of functionality. - Ł
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