Ubuntu 18.04: Couldn't load SIP module qgis

I am trying to install QGIS on Ubuntu 18.4 so I added this repo:

sudo add-apt-repository ppa:ubuntugis/ubuntugis-unstable
sudo apt-get update

Finally updated my sources and I installed QGis:

sudo apt update
sudo apt install qgis

but when running the application i got these errors:

groot@groot-Product:~$ qgis
"<font color=\"red\">Couldn't load SIP module.<br>Python support will be disabled.</font><br><pre><br>Traceback (most recent call last):<br>&nbsp; File \"<string>\", line 1, in <module><br>&nbsp; File \"/usr/lib/python3/dist-packages/qgis/__init__.py\", line 72, in <module><br>&nbsp; &nbsp; from qgis.PyQt import QtCore<br>&nbsp; File \"/usr/lib/python3/dist-packages/qgis/PyQt/QtCore.py\", line 26, in <module><br>&nbsp; &nbsp; from PyQt5.QtCore import *<br>ImportError: /usr/lib/x86_64-linux-gnu/libQt5Core.so.5: version `Qt_5.12' not found (required by /home/groot/.local/lib/python3.6/site-packages/PyQt5/QtCore.so)<br><br></pre>Python version:<br>3.6.7 (default, Oct 22 2018, 11:32:17) <br>[GCC 8.2.0]<br><br>QGIS version:<br>3.4.6-Madeira 'Madeira', exported<br><br>Python path:<br>['/usr/share/qgis/python', '/home/groot/.local/share/QGIS/QGIS3/profiles/default/python', '/home/groot/.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/groot/.local/lib/python3.6/site-packages', '/usr/local/lib/python3.6/dist-packages', '/usr/lib/python3/dist-packages']"
"<font color=\"red\">An error occurred during execution of following code:<br><tt>qgis.utils.uninstallErrorHook()</tt></font><br><pre><br>Traceback (most recent call last):<br>&nbsp; File \"<string>\", line 1, in <module><br>NameError: name 'qgis' is not defined<br><br></pre>Python version:<br>3.6.7 (default, Oct 22 2018, 11:32:17) <br>[GCC 8.2.0]<br><br>QGIS version:<br>3.4.6-Madeira 'Madeira', exported<br><br>Python path:<br>['/usr/share/qgis/python', '/home/groot/.local/share/QGIS/QGIS3/profiles/default/python', '/home/groot/.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/groot/.local/lib/python3.6/site-packages', '/usr/local/lib/python3.6/dist-packages', '/usr/lib/python3/dist-packages']"

And after I exit the application I got these error:

"<font color=\"red\">An error occurred during execution of following code:<br><tt>qgis.utils.uninstallErrorHook()</tt></font><br><pre><br>SystemError: PyEval_EvalCodeEx: NULL globals<br><br></pre>Python version:<br><br><br>QGIS version:<br>3.4.6-Madeira 'Madeira', exported<br><br>Python path:<br>"
groot@groot-Product:~$ 

I found a solution for my problem so i answered to my question to someone stuck in my situation:

According this page on Stack Overflow:

PyQt in PyPI is not compatible with the installed Qt

So I removed pyqt5 using pip3:

pip3 uninstall PyQt5

and installed PyQt5 from apt:

sudo apt-get install python3-pyqt5

Now Qgis seems to work correctly.