** Edited post to hopefully clarify what I’m trying to accomplish and what I’ve done so far.
Problem
I am trying to create a custom widget which can perform it’s own cleanup tasks before it is fully destroyed, but triggered by the application closing. I want to do this because my QWidget creates a temporary file on my PC that I want it to delete, but this can also be used for other threads or processes that are created and managed entirely by a child QWidget.
Here is the basic idea of what I am trying to do:
class MyCustomWidget(QTableWidget):
"""This could be any kind of widget.
I picked a table widget so something would show up.
"""
def __init__(self, parent=None):
super().__init__(parent=parent)
self._temp_filepath = temporary_file.txt
def create_file(self):
with open(self.temp_file_path, 'w') as file:
file.write(<contents of file>)
def _cleanup(self):
try:
os.path.remove(self.temp_file_path)
except OSError:
pass # Silently ignore cleanup errors
class MainWindow(QMainWindow):
"""Custom QMainWindow."""
def __init__(self):
super().__init__()
central_widget = QWidget()
layout = QVBoxLayout(central_widget)
self.setCentralWidget(central_widget)
self.my_custom_widget = MyCustomWidget(parent=self)
layout.addWidget(self.my_custom_widget)
button = QPushButton('Create File')
button.clicked.connect(self.my_custom_widget)
layout.addWidget(button)
if __name__ == '__main__':
app = QApplication(sys.argv)
main_window = QMainWindow()
main_window.show()
sys.exit(app.exec())
How do I get MyCustomWidget._cleanup() to run when I hit the Red X or otherwise close the application?
Attempted Solutions
class MyCustomWidget(QTableWidget):
"""This could be any kind of widget.
I picked a table widget so something would show up.
"""
def __init__(self, parent=None):
super().__init__(parent=parent)
self._temp_filepath = temporary_file.txt
# Catch destroyed signal and call cleanup
self.destroyed.connect(self._cleanup)
# This signal doesn't get emitted in time to be useful.
def create_file(self):
with open(self.temp_file_path, 'w') as file:
file.write(<contents of file>)
# I've learned that closeEvent is only available to the top-level.
# In this case, my MainWindow class.
def closeEvent(self, event):
self._cleanup()
event.accept()
def _cleanup(self):
try:
os.path.remove(self.temp_file_path)
except OSError:
pass # Silently ignore cleanup errors
The destroyed signal is not emitted in time to call the _cleanup() function. closeEvent() is only available to top-level widgets. i.e. my MainWindow class.
Known, But Unwanted Solutions
These are options that I know can work, but I’d like to not use because I want the child to cleanup after itself and not require a parent to tell it to (story of my life right?):
class MainWindow(QMainWindow):
def __init__(self):
super().__init__()
central_widget = QWidget()
layout = QVBoxLayout(central_widget)
self.setCentralWidget(central_widget)
self.my_custom_widget = MyCustomWidget(parent=self)
layout.addWidget(self.my_custom_widget)
button = QPushButton('Create File')
button.clicked.connect(self.my_custom_widget)
layout.addWidget(button)
# I don't want to have to tell the widget to clean up.
def closeEvent(self, event):
self.my_custom_widget._cleanup()
event.accept()
if __name__ == '__main__':
app = QApplication(sys.argv)
main_window = QMainWindow()
main_window.show()
# Again, I don't want to have to tell the widget to cleanup.
app.aboutToQuit.connect(main_window.my_custom_widget._cleanup)
sys.exit(app.exec())
I also know that I can more explicitly manage the lifecycle of the file, but this concept is extendable to other uses like stopping a watchdog thread which is created and managed by the child widget.