<![CDATA[pyside6-designer can't load PySidePlugin.dll (custom widgets)]]>When running in a virtual environment pyside6-designer fails to load custom widgets.

Custom widgets only load when the 'base' Python folder is in the path.

Note that this 'base' Python folder can be found with sys._base_executable.

Please make pyside6-designer such that it can load custom widgets without the need for the 'base' Python folder being in the PATH.

Reproduce with;

Running Python 3 (tested 3.9 - 3.11 64 bit) on Windows (tested 11).

Create a virtual environment.

pip install PySide6.

Run pyside6-designer.

TicTacToe widget is not available. Help->About Plugins shows error loading PySidePlugin.dll.

Sysinternals DebugView shows no messages.

Add the folder holding the base Python executable (C:\Program Files\Python3XX) to the path.

Run pyside6-designer.

Now the TicTacToe widget is available

2a2e8554-f695-4121-b983-504cba55b507-image.png
d2b6452e-1692-428e-a318-b9f4343fc9a7-image.png

]]>https://forum.qt.io/topic/140388/pyside6-designer-can-t-load-pysideplugin-dll-custom-widgetsRSS for NodeWed, 23 Sep 2026 10:03:50 GMTFri, 28 Oct 2022 14:56:17 GMT60<![CDATA[Reply to pyside6-designer can't load PySidePlugin.dll (custom widgets) on Wed, 02 Nov 2022 10:25:38 GMT]]>The tool wrapper can arguably add it Prospective fix ..

]]>https://forum.qt.io/post/734821https://forum.qt.io/post/734821Wed, 02 Nov 2022 10:25:38 GMT<![CDATA[Reply to pyside6-designer can't load PySidePlugin.dll (custom widgets) on Sun, 30 Oct 2022 15:35:28 GMT]]>@friedemannkleint Note that other libs also need stuff from the 'base' Python folder but do not need the 'base' Python folder being in the PATH.
Note that sys._base_executable can be used to find this folder. pyside6-designer could add this folder itself.

]]>https://forum.qt.io/post/734541https://forum.qt.io/post/734541Sun, 30 Oct 2022 15:35:28 GMT<![CDATA[Reply to pyside6-designer can't load PySidePlugin.dll (custom widgets) on Sat, 29 Oct 2022 20:18:03 GMT]]>I don't think this can be fixed. Qt Designer needs to be able to load the complete DLL including its dependencies (python.dll). This happens in the library loader in C++; there is no Python involved.

]]>https://forum.qt.io/post/734501https://forum.qt.io/post/734501Sat, 29 Oct 2022 20:18:03 GMT<![CDATA[Reply to pyside6-designer can't load PySidePlugin.dll (custom widgets) on Fri, 28 Oct 2022 17:09:35 GMT]]>@Okko-Willeboordse said in pyside6-designer can't load PySidePlugin.dll (custom widgets):

Please make pyside6-designer such that it can load custom widgets without the need for the 'base' Python folder being in the PATH.

If you want this you need to ask developers or raise as Qt bug.

]]>https://forum.qt.io/post/734417https://forum.qt.io/post/734417Fri, 28 Oct 2022 17:09:35 GMT