[Python-Dev] Remove typing from the stdlib (original) (raw)

Paul Moore p.f.moore at gmail.com
Tue Nov 7 06:30:11 EST 2017

On 7 November 2017 at 10:18, Steve Holden <steve at holdenweb.com> wrote:

On Tue, Nov 7, 2017 at 12:35 AM, Donald Stufft <donald at stufft.io> wrote: [..]

Maybe we just need to fully flesh out the idea of a "Python Core" (What exists now as “Python”) and a “Python Platform” (Python Core + A select set of preinstalled libraries). Then typing can just be part of the Python Platform, and gets installed as part of your typical installation, but is otherwise an independent piece of code. Given that (type and other) annotations have been promoted as an optional feature of the language it seems unfair and perhaps unwise to add a dependency specifically to support them to the stdlib and therefore the Python core. Since type annotations are, as Paul pointed out, development-time features, it would appear to behoove those wishing to use them to separate them in such a way that the software can be installed without annotations, and therefore without the need for the typing module. Assuming they would like to see the widest possible distribution, of course. For selected audiences I am sure typing will be de rigeur,

From my point of view, I take the same premise and come to the opposite conclusion.

Because type annotations are a development-time feature, they should not require a dependency in the final deployment (apart from Python itself). However, because they are a language syntax feature they are of necessity written in the application source. And type specification of anything more complex than basic types (for example, List[int]) requires classes defined in the typing module. Therefore, typing must be in the stdlib so that use of type annotations by the developer doesn't impose a runtime dependency on the end user.

If there were a way of including type annotations that had no runtime effect on the final deployed program, things would be different. But the decision to make annotations part of the language syntax precludes that. In particular, "it would appear to behoove those wishing to use them to separate them" - there's no way of doing that precisely because they are a language syntax feature.

Paul

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