SIP failed to load Ubuntu 20.04.1 QGIS 3.16.1

Question

Recently I updated my Ubuntu to 20.04.1 and QGIS to 3.16.1. If I start QGIS now I get this message:

Das SIP-Modul konnte nicht geladen werden.
Die Python-Unterstützung wird abgeschaltet.


Traceback (most recent call last):
  File "", line 1, in 
  File "/usr/lib/python3/dist-packages/qgis/__init__.py", line 70, in 
    from qgis.PyQt import QtCore
  File "/usr/lib/python3/dist-packages/qgis/PyQt/QtCore.py", line 24, in 
    from PyQt5.QtCore import *
ImportError: /home/kai/.local/lib/python3.6/site-packages/PyQt5/QtCore.so: undefined symbol: _ZdlPvm, version Qt_5


Python-Version:
3.6.9 (default, Oct  8 2020, 12:12:24) 
[GCC 8.4.0]

QGIS-Version:
3.16.1-Hannover 'Hannover', b381a90dca

Python-Pfad:
['/usr/share/qgis/python', '/home/kai/.local/share/QGIS/QGIS3/profiles/default/python', '/home/kai/.local/share/QGIS/QGIS3/profiles/default/python/plugins', '/usr/share/qgis/python/plugins', '/usr/lib/python36.zip', '/usr/lib/python3.6', '/usr/lib/python3.6/lib-dynload', '/home/kai/.local/lib/python3.6/site-packages', '/usr/local/lib/python3.6/dist-packages', '/usr/lib/python3/dist-packages']

The question I found is over 8 years old, is there now a day an easy solution?

---

If i execute this command:

ls /usr/bin | grep python

i got these lines back

dh_python2
python
python2
python2.7
python2.7-config
python2-config
python3
python3.8
python3.8-config
python3-config
python3-futurize
python3-pasteurize
python-config
x86_64-linux-gnu-python2.7-config
x86_64-linux-gnu-python2-config
x86_64-linux-gnu-python3.8-config
x86_64-linux-gnu-python3-config

At the error message python version 3.6.9 is searched.

Is my python too new for QGIS?

Answer 1

Use virtual environment for spyder or QGIS, not use the same for both.

In addition, your QGIS is using the local python installed, rename the local file directory and try again (QGIS and Spyder).

Try this:

mv /home/kai/.local/lib/python3.6 /home/kai/.local/lib/bkcup_python3.6

Then, try to launch QGIS and Spyder. If not works, undo the changes and continue searching for solution.

Answer 2

A solution that work for me...

Try to execute this command

pip3 uninstall pyqt5 pyqt5-sip qtconsole

now QGis starts without any errormessages.

I also use Spyder V.4, if i unistall these packages spyder wont start anymore. If i execute

pip3 install spyder

spyder will open but qgis dosent.

Did anyone know why these to programms interfere each other ? Is a "peacefull" use of booth possibly ?