Python bindings using cppyy (was: An update on Python bindings)

Shaheed Haque srhaque at
Mon Nov 5 15:19:45 GMT 2018

I'm afraid that there has been no progress as I am buried in "startup"
mode. I'm not sure when that might change.

On Mon, 5 Nov 2018, 14:02 Philipp A. <flying-sheep at wrote:

> Hi Shaheed!
> The year is nearing its end, and I wonder if there has been any progress
> and/or if you people need help with the bindings!
> I’d really like to revive my IPython console in Kate :D
> Best, Philipp
> Shaheed Haque <srhaque at> schrieb am Sa., 13. Jan. 2018 um
> 19:06 Uhr:
>> Thanks to some upstream fixes, I have the cppyy-based bindings for KF5
>> and also Qt5 (see below) showing signs of life. Notes:
>>    1. The packaging has advanced to the point where I think ECM-based
>>    framework-by-framework bindings are a real possibility, with both Py2 and
>>    Py3. AFAICS, this addresses the main feedback received to date.
>>    2. With reference to the remark about tracking dependencies between
>>    frameworks, apologies for the delayed response as I somehow missed
>>    the email. I note that the dependencies currently in CMake often seem
>>    incomplete. I'll bring that to the community separately.
>>    3. There is one issue still open upstream (
>>    However, I don't consider this to be a showstopper...we might even be able
>>    to live with it as is.
>>    4. For me, the jury is still out on PyQt versus a new set of
>>    cppyy-based Qt bindings. Clearly PyQt is solid and mature, but the
>>    limitations really concern me (if anybody wants to know more, I'm happy to
>>    discuss, but let's do that in another thread please). Now, given that there
>>    are examples in the wild of interoperating cppyy/cling/ROOT with PyQt, I'm
>>    going to sidestep this question but am playing with a cppyy-based approach.
>>    At this point, all of Qt has basic cppyy-based bindings, and the next step
>>    is to tackle things like finding a way to express the object
>>    ownership/destruction rules in a more-or-less systematic way.
>>    5. On the P2/P3 question, I'm presently still committed to both P2
>>    and P3. I *have* had a couple of minor occasions where P3-only might have
>>    been nice *for my code*, but if I do find an issue that tips the balance,
>>    or I find some serious benefit *for the bindings*, I'll drop P2. One
>>    possible such benefit would be if I can see a sane way to address PEP484
>>    type hints.
>> To get here, I had to build a subset of the tooling I previously had
>> developed for the SIP-based approach. The big difference is the absence of
>> any need to support customisation of the generated bindings. I am hopeful
>> that in the worst case, there might be some minimal customisation (known as
>> Pythonisations in cppyy parlance) such as for #4 above, but nothing like
>> the scale needed for SIP.
>> The core tooling is not specific to KF5 or KDE or Qt5, and is developed
>> in upstream cppyy over on The core tooling is built
>> around CMake, notably for the generation phase and the C++ library build.
>> The PoC extends the core tooling with Pythonic packaging and installation
>> using pip/wheels, also from CMake. As before I would look for help to get
>> an ECM equivalent, possibly based on the same approach but perhaps
>> including CI and distribution via PyPi.
>> Finally, now would be a good time for anybody else who wants to get
>> involved to step up, especially as a new job limits my free time.
>> Thanks, Shaheed
>> P.S. Not to stoke the the P2/P3 wars unnecessarily, but while I know that
>> upstream Clang just added P3 support in the clang 5.0 release, current
>> Ubuntu only packages it for 2.7.14. So I won't be moving yet...
>> On 5 November 2017 at 13:23, Boudewijn Rempt <boud at> wrote:
>>> On Sat, 4 Nov 2017, Chris Burel wrote:
>>> > I think this is a remarkably short sighted statement. It assumes that
>>> people that would use these bindings have no existing Python codebase at
>>> all, and can afford to start a brand new project. The reality is much
>>> different.
>>> >
>>> > Let's take a specific example. I have 6 years experience writing
>>> Python for the visual effects industry. We have a 10 year old Python 2
>>> codebase. We also use an application from Autodesk called Maya. It has been
>>> a Qt 4 application with Python 2 embedded since 2012. In 2016 they jumped
>>> to qt 5 and pyside2. Now Autodesk knows that companies have built large
>>> codebase around their product that requires Python 2. What would've
>>> happened if pyside2 did not support Python 2.7? They'd be stuck either
>>> forcing all their customers to move to Python 3 and risk people not wanting
>>> the new version of the software, or they'd be prevented from moving to Qt 5.
>>> >
>>> You will have to switch to Python 3 by 2019, since that's what the VFX
>>> Reference Platform says. If you haven't started on the migration yet,
>>> you're very late. And the VFX Refernece Platform is basically Autodesk
>>> telling the rest of the industry what to use, including their weird
>>> patchset for Qt...
>>> > So no, Python 2 is not dead. Not by a long shot.
>>> For VFX, it will be dead in 2019. See
>>> --
>>> Boudewijn Rempt |,
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