On Fri, Jan 07, 2022 at 04:27:37PM -0800, Christopher Barker wrote:
> Note that if PEP 563 is ultimately accepted, then Annotations would be
> strings, and type checkers could use any language they wanted.
Annotations still have to be syntactically valid Python expressions.
>>> from __future__ import annotations
>>> def func(arg: array[1...10] of float) -> str: pass
File "<stdin>", line 1
def func(arg: array[1...10] of float) -> str: pass
^^^
SyntaxError: invalid syntax
Of course if you explicitly wrap your annotation in quotation marks, you
can use any syntax you like (think: regexes, SQL, etc). But without a
*standard* annotation syntax:
- static checkers will disagree on what annotations mean;
- runtime introspection will be difficult; and
- IDEs and syntax colourisers are going to just treat them as strings.
We can write little DSLs with any syntax we like using explicitly quoted
strings. We're not limited to do this in annotations. But while DSLs
tend to be specific to your own library or application, annotations
exist in a wide ecosystem of both static and runtime tools that expect
to interpret annotations.
Writing your own little DSL for annotations cuts you off from the rest of the
Python
ecosystem.
--
Steve
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