Can't stop in subthread's breakpoint when debugging.

[MyronCodes]

This is the test code.
The Thread class is a sub thread.
When I make a breakpoint in app = QApplication(sys.argv). I can stop when I debugging.
But when the breakpoint is in Thread's def run(self): , then code will run and print but didn't stop.

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

# ----- ----- ----- ----- ----- <[ Sys ]> ----- ----- ----- ----- ----- #

import os
import sys
import time
import pynput

# ----- ----- ----- ----- ----- <[ PyQt5 ]> ----- ----- ----- ----- ----- #

from PyQt5.QtWidgets import *
from PyQt5.QtCore import *

class Thread(QThread):

    qt_signal = pyqtSignal(str)

    def __init__(self, parent = None):
        super().__init__(parent)
        print('Thread init')

    def run(self): 
        time.sleep(1)
        for i in range(10):
            print('Thread run')

class Basic(QMainWindow):

    def __init__(self):
        super().__init__()
        self.sub = Thread()
        self.sub.start()

app = QApplication(sys.argv)
ui = Basic()
sys.exit(app.exec_())

[karthiknadig]

Qt use native threads to start the thread. Python itself is unaware of these, you will need to use debugpy.debug_this_thread() API in run to debug it https://github.com/microsoft/debugpy/wiki/API-Reference#debug_this_thread

[int19h]

It should also work if you enable Qt support; but it might require specifying the Qt package you're using explicitly, if you have more than one installed. Something like:

"qt": "pyside2"
"qt": "pyqt5"

[fabioz]

As a note, when using the frame eval mode in the debugger (on Python 3.6 onwards with compiled extensions), this should work out of the box now.

Closing since there doesn't seem like there's anything else to be done here.

[Bwijn]

Solution for Debugging QThread in PySide6 with Debugpy

If you're working with PySide6 and encountering issues while trying to debug a QThread, you're not alone. Many users face challenges when trying to debug threads in Qt applications. Here's a solution that worked for me using debugpy to connect to the thread and set breakpoints.

Problem:
When debugging QThread in PySide6, breakpoints inside the run() method don't trigger

Solution:
`import sys
import time
from PySide6.QtWidgets import QApplication, QWidget, QVBoxLayout, QLabel, QPushButton
from PySide6.QtCore import QThread, Signal, Slot
import debugpy
class WorkerThread(QThread):

task_finished = Signal(int)

def __init__(self, thread_id, parent=None):
    super().__init__(parent)
    self.thread_id = thread_id

def run(self):
    debugpy.breakpoint()  # set here breakpoint !!!!!!!!!!!!!!!!!!!!!!!!!!!!Explicitly set!!!!!!!!!!!!!!!!!!!!

    print(f"Thread {self.thread_id} starting")
    time.sleep(2)  
    print(f"Thread {self.thread_id} finished")
    self.task_finished.emit(self.thread_id)