Bug 2139884

Summary: Simple PyQt5 application prints "QSocketNotifier: Can only be used with threads started with QThread"
Product: [Fedora] Fedora Reporter: Andrew Pitonyak <andrew>
Component: python-qt5Assignee: Rex Dieter <rdieter>
Status: NEW --- QA Contact: Fedora Extras Quality Assurance <extras-qa>
Severity: low Docs Contact:
Priority: unspecified    
Version: 37CC: aligoldenhat, andrew, kde-sig, projects.rg, rdieter, than
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Hardware: x86_64   
OS: Linux   
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Description Andrew Pitonyak 2022-11-03 17:33:30 UTC 
This is Bug 1967402 opened against Fedora 34, which is EOF so the bug was closed. Bug still exists in Fedora 37. Original report reads as follows: 

PyQt5 applications print out "QSocketNotifier: Can only be used with threads started with QThread" when executed.

Version-Release number of selected component (if applicable): 5.15.0-8.fc34


How reproducible:
Always happens on my system.

Steps to Reproduce:
Execute the following Python code.

import sys
from PyQt5.QtWidgets import QApplication, QLabel

app = QApplication(sys.argv)
label = QLabel('Hello World!')
label.show()
sys.exit(app.exec())


Actual results:
The terminal shows "QSocketNotifier: Can only be used with threads started with QThread" when the program starts.

Expected results:
Nothing should be printed.


I also see the problem using

import matplotlib.pyplot as plt
fig, ax = plt.subplots()

This is part of a larger program that then does not show a graphic. Note that I am using Wayland.
Comment 1 aligoldenhat 2023-07-12 14:52:24 UTC 
I also have this bug on frdora 38 

And i get this result in terminal:
QSocketNotifier: Can only be used with threads started with QThread
qt.qpa.qgnomeplatform.theme: The desktop style for QtQuick Controls 2 applications is not available on the system (qqc2-desktop-style). The application may look broken.