Can you catch a PyQt5 "fail fast exception" in Python?

Question

Usually, if you call a non-existing method on a PyQt5 object, like calling .show() on a boolean variable as in the click handler below, which is an example that will always trigger an exception:

import sys, os
from PyQt5.QtWidgets import QApplication, QMainWindow, QPushButton

class MainWindow(QMainWindow):
  def __init__(self):
    super().__init__()
    print("Hello from MainWindow")
    self.setWindowTitle("My App")
    button = QPushButton("Press me!")
    button.clicked.connect(self.button_clicked)
    self.setCentralWidget(button)
  def button_clicked(self, s):
    print("click", s)
    s.show()

def main(argv=None):
  app = QApplication(sys.argv)
  window = MainWindow()
  window.show()
  try:
    app.exec()
  except:
    print("Exception")

if __name__ == '__main__':
    main()

So when I click the button in this example, I get:

---------------------------
My App: python3.exe - Fail Fast Exception
---------------------------
A fail fast exception occurred. Exception handlers will not be invoked and the process will be terminated immediately. 
---------------------------
OK   
---------------------------

Ok - but if I wrap the app.exec() in try ... catch block, - obviously, - it does not catch this exception (probably because its from a C++ PyQt5 object)?

So, my question is: can I somehow catch/handle this kind of an exception in python (but hopefully somewhere "down the chain", as in trying to catch any such application exception with a single statement, as I've tried to do with try ... catch around app.exec())?

Answer 1

Try it:

import sys
from PyQt5.QtWidgets import QApplication, QMainWindow, \
    QPushButton, QMessageBox
    

class MainWindow(QMainWindow):
  def __init__(self):
    super().__init__()
    print("\nHello from MainWindow")
    self.setWindowTitle("My App")
    
    button = QPushButton("Press me!")
    button.clicked.connect(self.button_clicked)
    self.setCentralWidget(button)
    
  def button_clicked(self, checked):
    print(f"\nbutton checked: {checked}\n")
    checked.show()

# +++ vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
import traceback
def except_hook(exc_type, exc_value, exc_tb):
    tb = "".join(traceback.format_exception(exc_type, exc_value, exc_tb))
    msg = QMessageBox.warning(
        None, 
        'Attention! ERROR!', 
        f'{tb}' 
    )        
# +++ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

if __name__ == '__main__':
    app = QApplication(sys.argv)
  
    sys.excepthook = except_hook                              # +++ <----
      
    window = MainWindow()
    window.show()
    exit(app.exec())