PyQt6: DLL load failed while importing QtGui: The specified procedure could not be found.

[tanzi]

My Environment

• OS: Windows 10
• Python: 3.9.9
• Anaconda: Anaconda3-2022.05-Windows-x86_64
• vitual environment: base,PyQt6
• The output of the command pip list when the virtual environment is "PyQt6":

  Package          Version
  ---------------- ---------
  click            7.1.2
  pip              21.3.1
  PyQt6            6.1.0
  pyqt6-plugins    6.1.0.2.2
  PyQt6-Qt6        6.3.1
  PyQt6-sip        13.4.0
  pyqt6-tools      6.1.0.3.2
  python-dotenv    0.20.0
  qt6-applications 6.1.0.2.2
  qt6-tools        6.1.0.1.2
  setuptools       60.5.0
  wheel            0.37.1
  

• The output of the command pip list|findstr "Qt" when the virtual environment is "base"

  PyQt6                         6.3.1
  PyQt6-Qt6                     6.3.1
  PyQt6-sip                     13.4.0
  QtAwesome                     1.0.3
  QtPy                          2.0.1
  

The issue

When the vritual environment is "PyQt6", the code from PyQt6 import QtWidgets throws the error below

DLL load failed while importing QtGui: The specified procedure could not be found.

But, when the vritual environment is "base", the code runs normally

Why?How to solve it?

[tanzi]

Another test

First step, create a brand-new virtual environment, and then install PyQt6

conda create -n PyQt6_2 python=3.9.9
conda activate PyQt6_2
pip install PyQt6

Then, test the code from PyQt6 import QtWidgets

Python
>> from PyQt6 import QtWidgets

Everything runs fine now.

Second step, install PyQt6-tools

pip install PyQt6-tools

Then, the code from PyQt6 import QtWidgets will throw the error PyQt6: DLL load failed while importing QtGui: The specified procedure could not be found.

Comparsion

Before I installed PyQt6 , the output of pip list was

Package    Version
---------- -------
pip        21.3.1
PyQt6      6.3.1
PyQt6-Qt6  6.3.1
PyQt6-sip  13.4.0
setuptools 60.5.0
wheel      0.37.1

After I installed PyQt6 , the output of pip list was

Package          Version
---------------- ---------
click            7.1.2
pip              21.3.1
PyQt6            6.1.0
pyqt6-plugins    6.1.0.2.2
PyQt6-Qt6        6.3.1
PyQt6-sip        13.4.0
pyqt6-tools      6.1.0.3.2
python-dotenv    0.20.0
qt6-applications 6.1.0.2.2
qt6-tools        6.1.0.1.2
setuptools       60.5.0
wheel            0.37.1

The tests on base and PyQt6 virtual environments are the same with this test.

• In the first test, the virtual environment base installed PyQt6 and not installed PyQt6-tools

[JonB]

@tanzi
Sounds potentially like a "DLL found but required symbol within DLL not found", an inconsistency within the C++ Qt DLLs or between them and PyQt6. I would search my whole disk for e.g. dir /s/b Qt*.DLL. Any mixed versions? Any Qt5 artefacts? What version of PyQt6 versus Qt6 do you see?

[Plinio B]

the problem starts on PyQt version 6.0.3. Do not install other modules that depends on the version above 6.03. I solve the issue by installing PyQt 6.0.2 and pyqt6-tools 6.0.2

my version list is the following

Package Version

---

click 7.1.2
pip 21.3.1
PyQt6 6.0.2
pyqt6-plugins 6.0.2.2.2
PyQt6-Qt 6.0.1
PyQt6-Qt6 6.0.2
PyQt6-sip 13.4.0
pyqt6-tools 6.0.2.3.2
python-dotenv 0.20.0
qt6-applications 6.0.2.2.2
qt6-tools 6.0.2.1.2
setuptools 60.2.0
wheel 0.37.1