[PySide] Python bindings for Qt/C++ library (advice needed on best practices)

[Alexandru Croitor]

Hi,

For 1) if the bindings for your library don't expose any Qt classes to Python, then yes, you don't need to ship the QtCore python module, etc. You do need QtCore and QtXmlPatterns for building and running shiboken though. But deployment wise, you will only need Qt libraries and libshiboken, and the generated module for your library. You won't need PySide2 libraries.

For 2) it's more of a deployment question, which for now users have to figure out for themselves based on their use cases. PyInstaller helps in this respect. And if you plan to publish your bindings to PyPi, I suspect there is some way (requirements.txt or similar) to specify that the PySide2 package needs to be installed as well.
> On 19. Jul 2018, at 02:10, info at mycontent.gr wrote:
> 
> Dear all,
> 
> first of all congratulations and thanks to the PySide2 team for a great project.
> 
> After going through the blog post at http://blog.qt.io/blog/2018/05/31/write-python-bindings/ on creating Python bindings for a C++ library with Shiboken, a few questions arise when thinking about a bigger/real-life project. I suspect these questions will come up frequently as people try to build Python bindings for their projects, so I would like to volunteer to collect the answers that I hope to get from this mailing list into a tutorial-style document (if the team is interested in this!)
> 
> Suppose that we have a Qt-based C++ library, for which we would like to create Python bindings.
> Many library classes are subclasses of QObject. There are several methods accepting QString arguments and returning QLists, QHashes, QMaps, as well as pointers to the library’s objects.
> Suppose that the library uses QtSql and QtXml (and many elements of QtCore) internally, but these objects need not be exposed to the user.
> In most use cases, the users of the bindings will not need the Qt user interface classes, as they will be writing automation scripts. The library itself does not depend on QtGui, QtWidgets etc.
> 
> What would be the best course of action:
> 1. Write a thin interface layer to the library using only C++ primitives and STL types, like std::string, std::list, so that all interfaces that will be exposed to Python accept and return standard library constructs?
> 2. Create Python bindings with Qt objects as arguments?
> 
> In the first case, how can we keep the dependencies for library users to a minimum? QtCore, QtSql and QtXml are necessary for the functioning of the library, but the Python bindings of these Qt libraries, normally should not be necessary (is this correct?).
> In the second case, how can we package the library in such a way that the required PySide2 dependencies are installed automatically (preferably using pip)? How can we keep the dependencies to a minimum?
> 
> Thank you very much for your time!
> 
> Kind regards,
> 
> George Christodoulides
> 
> 
> 
> 
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