PySide is a Python binding for the Qt framework that was developed by INdT to provide Python bindings under the LGPL license. It consists of PySide, which is imported, libpyside which handles Qt signals and slots, and libshiboken which helps interface Python and C++. Shiboken is the binding generator used to create the PySide bindings and can generate bindings for any C++ library. Currently, many Qt modules like QtCore and QtGui are supported. Future work includes improving the binding generation process and expanding platform support.

1. PySide
Python Bindings for the Qt Framework
Marcelo Lira - setanta
March, 10th / Manaus - AM

2. Prologue

3. Who Am I?
• Paid Open Source developer (lucky me!)
• Computer Engineering Undergrad
• I like Python but code mostly in C++
(it’s the "binding developer paradox")
• PySide / PyMaemo team member at INdT

4. Who We Are?
• INdT - Instituto Nokia de Tecnologia
• openBossa - INdT’s open source stream
• Known projects: Canola, Carman, PyMaemo
• Friends of Qt Development Frameworks / KDE

5. Qt Labs Americas
• openBossa initiative
• Development of Qt and KDE communities on the
Americas
http://qtlabs.openbossa.org

6. Python
"Python is the best language ever invented!" -- me
import antigravity

7. Qt Frameworks
Cross-platform application development framework.
A little while after Nokia’s acquisition of Trolltech Qt started being
distributed under the LGPL license.

8. Today’s Topics
• PySide
• Binding Generation
• Current Status
• Future

10. PySide == Python + Qt
PySide is how we call the Python bindings of the Qt
Framework produced by INdT/openBossa/Qt Labs
Americas and released under the LGPL license.

11. PySide Motivation
Python bindings for Qt under the LGPL license, aligned
with the new licensing of Qt.
Make the Qt-Python bindings fit
hand-in-glove on the Maemo platform
and devices.
Because we are the INdT.

12. PySide Overview
• PySide: the thing that you import
• libpyside: takes care of Qt signals/slots
• libshiboken: helps interfacing Python with C++

13. Binding Assembly Line
• Qt Headers: the basic information about Qt libraries comes
from here.
• Type System files: here the binding developer modifies the
collected information to fit the Python language.
• Handwritten code: code to handle the C++ idiosyncrasies
that could appear.

14. And Why Not...?
• Cython
• ctypes
• Swig
• SIP
• SMOKE
• Boost.Python
• My favorite technology...

15. Binding Generation

16. PySide Goals
Besides delivering LGPL Python bindings for Qt, our
other important goal was to deliver the complete
binding factory.
fishes + fishing rod
or
PySide + Binding Generator
And we care about your fishing skills too, so we try to
document every part of the system.

17. Binding C++ libraries
Things one must take care in the binding business:
• C++ object to Python wrapper association
• Inheritance
• Multiple inheritance and casting pointers
• Implicit type conversions
• Methods with multiple signatures
• Protected methods
• Function arguments that return values
• Virtual method overrides
• Object ownership

18. Shiboken
• Shiboken is the binding generator used to create
the PySide bindings.
• It can generate bindings not only for Qt, but for
any C++ library.
• The word means nothing at all. I was trying to
remember some name and instead of returning an
empty string my brain made that up.

19. Shiboken
Ok, if you really need a meaning...
• Shi: Death
• Bo: Something, someone or somewhere
• Ken: Sword
(Disclaimer: I don’t know Japanese.)

20. Binding Generator Pedigree

21. Boost.Python
The code created by the first Python binding generator used
Boost.Python as sugar coating over the C Python API.
In the beginning it was good because:
• Quick start
• Runtime speed
Nevertheless, there was a bad part that showed up later:
• The size problem
templates over templates over templates == huge binaries
• Lack of flexibility
indirect access to the C Python API became a
problem when flexibility was needed.

22. Binding Assembly Line (Again)
• API Extractor: collects information from library headers, merges it with
the modifications and handwritten code defined in the type system
description.
• Generator Runner: dynamic loader of generator front-ends.
• Shiboken: generator front-end that outputs CPython source code.

23. libshiboken
Bindings generated with Shiboken will also need
libshiboken (which is LGPL, by the way).
libshiboken helps with:
• Association of C++ objects
with Python wrappers
• Multiple inheritance
• Implicit type conversions
• Virtual method overrides
• Object ownership

24. The Type System Description
<typesystem package="sample">
<primitive-type name="int"/>
<primitive-type name="Complex" target-lang-api-name="PyComplex">
<conversion-rule file="complex_conversions.h"/>
<include file-name="complex.h" location="global"/>
</primitive-type>
<namespace-type name="SampleNamespace"/>
<value-type name="Number" />
<value-type name="SimpleFile">
<modify-function signature="open()">
<modify-argument index="return">
<remove-argument/>
</modify-argument>
<inject-code class="target" position="end" file="simplefile_glue.cpp"/>
</modify-function>
</value-type>
</typesystem>

25. Current Status

26. Getting Rid of Boost.Python
Die Boost.Python!
Die!

27. Working Qt Modules
• QtCore
• QtGui
(almost done)
• QtNetwork and QtSvg
(community effort! Go cgoncalves!)
• QtWebkit
• QtTest

28. And Now What?
• Bug Fixing
A couple of important generator bugs must be
fixed.
• Release
We intend to release the Shiboken generated
PySide in a month from now.

29. Future

30. Better Generation Process
Help others to help themselves.
• A tool to quick start binding development.
• A visual binding creation/editing tool.
(Perhaps a QtCreator plugin.)

31. The Other Side
Our focus is on Maemo but there are other worlds we
care about.
• Linux Distros: were taken care by the community
(Cheers to odyx! And to chaz6 for the build patches.)
• MacOS X: it needs a little love. Anyone with a good
heart and a white laptop?
• Microsoft Windows: some work is already done,
but still needs love. Lovers?

32. Pythonization
One of PySide requisites was to be
API compatible with PyQt4.
But we want to make PySide’s API more Pythonic.
Great, but... what makes something Pythonic?
What is good?
What is right?
What is real?

33. PSEPs
PySide Enhancement Proposals
• Inspired by Python’s PEPs.
• Discussed with the community.

34. Questions?

35. Directions
www.pyside.org
http://lists.openbossa.org/listinfo/pyside
#pyside at Freenode
http://qt.gitorious.org/pyside
Marcelo Lira (setanta)
marcelo.lira@openbossa.org

36. Thanks
:)