The issue came up with trying to integrate parts of an existing Python3/Qt app (mikidown) into a Python2/Qt app. After minor standard issues, like exceptions and print functions, many strange errors with respect to QString and QVariant handling showed up.

Searching for solution considering the different unicode string handling between Py2 & Py3 did not give any answers: the solution lay in the different PyQt4 API versions for the different Python versions.

An introduction to the incompatible PySide API gave insight in how the different versions are handled and how the used API version can be switched for a given python environment.

The problems related to QString & QVariant could be solved by switching the API version for those two classes to the one which is standard in Python3.

The following snippet needed to be inserted before importing any Qt related module::

import sip
sip.setapi('QString', 2)
sip.setapi('QVariant', 2)

PySide only supports APIv2, I have to check PyQt5 as well.

My application for this is for the development of Markdown/reStructured text based wiki utilizing mikidown and ReText. Both target the Python3 but with the trick above, large number of issues were resolved.