Qt 5 to Qt 6 Migration Guide

Some notes and recommendations regarding the migration of Qt 5 to Qt 6, and PyQt 5 to PySide 6. Included in these notes are some external links to both official and unofficial sites.

Importing Qt modules

Until Katana 7.5 (last with Qt 5), Qt modules are imported with the following Python code:

from PyQt5 import QtCore, QtGui, QtWidgets

Since Katana 8.0 (first with Qt 6), the equivalent Python code is:

from PySide6 import QtCore, QtGui, QtWidgets

In order to support conditionally importing the Qt modules based on which version of Katana is being used, we recommend the following:

import KatanaInfo
katanaVersion = int(KatanaInfo.version.split('.')[0])
if katanaVersion >= 8:
  from PySide6 import QtCore, QtGui, QtWidgets
else:
  from PyQt5 import QtCore, QtGui, QtWidgets

Warning

It is discouraged to import the Qt modules using the widely known try/except ImportError pattern. If PyQt5 or PySide6 were available in the user’s system, and an attempt to import one of them in a version of Katana which doesn’t use it, Katana could wrongly succeed at importing them, leading to obscure fatal errors.

Qt 5 to Qt 6 Migration Notes

Qt have an extensive guide for migrating from Qt 5 to Qt 6, which can be found here:

https://doc.qt.io/qt-6/portingguide.html

The Python bindings for Qt largely follow the C++ Qt naming and structure. So changes listed above should, in most cases, apply equally to Python code. A good default strategy when coming up to issues in your Qt code, is to check the above guide for any mentions of the problematic Qt code. Another strategy worth mentioning is that Qt maintain API reference documentation for both their 5.x and 6.x lines. You can compare the API for a class in 5.x against 6.x. For example, the documentation for the QComboBox` class in Qt 5 can be found at

https://doc.qt.io/qt-5/qcombobox.html

Whereas the documentation for Qt 6 can be found at

https://doc.qt.io/qt-6/qcombobox.html

PyQt 5 to PySide 6 Migration Notes

At the time of writing this, no official and up-to-date migration documentation exists for porting PyQt 5 to PySide 6. The following may prove useful: