[Python-Dev] __signature__ for PySide ready

Nick Coghlan ncoghlan at gmail.com
Sat Aug 19 06:33:27 EDT 2017

On 19 August 2017 at 18:38, Christian Tismer <tismer at stackless.com> wrote:
> On 19.08.17 09:37, Nick Coghlan wrote:
>> Either way, the answer to Christian's original question is that "Yes,
>> supporting __signature__ is also useful in Python 2.x", as even though
>> the native inspect module doesn't support it, 3rd party backports do.
> I did not use a backport, but simply hacked it together, myself:
> - Take the signature part of Python 3.6 out,
> - Adjust the syntax to Python 2.7.

The backports we're talking about are the ones that can *read*
__signature__ attributes, as well as synthesise them from the
underlying attributes on Python level functions and code objects.

> The hairy part was my way to create the PySide PyCFunction objects in
> a compatible way like Python 3 does it: the handling of PyCFunction's
> "self" parameter is different (holds type info, Python 2 does not).
> That needed much more internal knowledge as intended...
> Well, I thought the existence of __signature__ might be a good reason
> to switch to Python 3, but if I support Python 2, the advantage
> is gone. But if it's ok with you, then I'll publish both versions.

The builtins and standard library extension modules in 2.7 will never
gain signature information (since there's no equivalent of Argument
Clinic to populate the __text_signature__ attributes).

However, aside from it being extra work that they may not want to do,
there's no particular reason for 3rd party modules to avoid providing
better signatures in Python 2.x.


Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia

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