[Python-Dev] PEP 544: Protocols - second round

Stéfane Fermigier sf at fermigier.com
Thu Jun 22 12:09:22 EDT 2017

On Thu, Jun 22, 2017 at 10:44 AM, Markus Wissinger <
markus.wissinger at gmail.com> wrote:

> Hi,
> I have to admit I am not happy with separating the concepts of 'runtime'
> and 'static' types as implied by pep544.
> I am currently exploring a type hint generator that produces hints out of
> types used in unit tests. It debugs the tests and collects the parameter
> types of call and return events. It ignores a type when a supertype is
> present. Failing isinstance/issubclass calls for protocols would hurt
> there. I understand that any type checker code that could provide
> isinstance functionality for pep544 protocols would rely on method
> signatures that my hint generator is just producing.
> proof of concept implementation (writes method docstrings, no pep484 type
> hints yet):
> https://github.com/markuswissinger/ducktestpy
> This is currently just some personal project that some of you will
> consider a strange idea.

Not a strange idea, I've had a similar idea and played a bit with it ~10
years ago (inspired by a Java project whose name eludes me now).

Also, I think PyCharm is able to do similar things (see


Stefane Fermigier - http://fermigier.com/ - http://twitter.com/sfermigier -
Founder & CEO, Abilian - Enterprise Social Software -
Chairman, Free&OSS Group / Systematic Cluster -
Co-Chairman, National Council for Free & Open Source Software (CNLL) -
Founder & Organiser, PyData Paris - http://pydata.fr/
“You never change things by fighting the existing reality. To change
something, build a new model that makes the existing model obsolete.” — R.
Buckminster Fuller
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