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Wed Nov 15 17:36:41 EST 2017 · https://mail.python.org/pipermail/python-dev/2017-November/150558.html

On 11/14/2017 3:26 PM, Ivan Levkivskyi wrote:
> After some discussion on python-ideas, see 
> https://mail.python.org/pipermail/python-ideas/2017-September/047220.html, 
> this PEP received positive comments. The updated version that takes into 
> account the comments that appeared in the discussion so far is available 
> at https://www.python.org/dev/peps/pep-0560/
> 
> Here I post the full text for convenience:
> 
> ++++++++++++++++++++++++++
> 
> PEP: 560
> Title: Core support for typing module and generic types
> Author: Ivan Levkivskyi <levkivskyi at gmail.com <mailto:levkivskyi at gmail.com>>
> Status: Draft
> Type: Standards Track
> Content-Type: text/x-rst
> Created: 03-Sep-2017
> Python-Version: 3.7
> Post-History: 09-Sep-2017
...

Suggested wording improvements:

> Performance
> -----------
> 
> The ``typing`` module is one of the heaviest and slowest modules in
> the standard library even with all the optimizations made.

> Mainly this is
> because of subscripted generic types (see PEP 484 for definition of terms
> used in this PEP) are class objects (see also [1]_).

Delete 'of' after 'because' to make this a proper sentence.

> The three main ways how

"There are three ..." reads better to me.

> the performance can be improved with the help of the proposed special 
> methods:
> 
> - Creation of generic classes is slow since the ``GenericMeta.__new__`` is
>    very slow; we will not need it anymore.
> 
> - Very long MROs for generic classes will be twice shorter;

I  believe by 'twice shorter', which is meaningless by itself, you mean 
'half as long'.  If so, please say the latter.
  > they are present
>    because we duplicate the ``collections.abc`` inheritance chain
>    in ``typing``.
> 
> - Time of instantiation of generic classes will be improved

Instantiation of generic classes will be faster.

>    (this is minor however).

-- 
Terry Jan Reedy

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[Python-Dev] PEP 560