what is the difference between `c = Controller(model, view)` and `Controller(model, view)` in python?

Question

I encontered a situation in my code and doubt it. I have a code like this:

def main():
    app = QApplication(sys.argv)
    view = View()
    db_name = 'db/main.db'
    model = Model(db_name)
    Controller(model, view)  # Connect the model and the view using the controller
    
    view.show()
    sys.exit(app.exec_())

if __name__ == '__main__':
    main()

but this wouldn't work as expected. I did this and it worked:

def main():
    app = QApplication(sys.argv)
    view = View()
    db_name = 'db/main.db'
    model = Model(db_name)
    c = Controller(model, view)  # Connect the model and the view using the controller
    
    view.show()
    sys.exit(app.exec_())

if __name__ == '__main__':
    main()

notice that I am not using the c variable. what I don't understand is what is the difference in the code, I am calling the controller and I think it should work, what I am missing here?

I searched it but I want to gain some insight about the internal work of it.

Answer 1

When you don't affect it to a variable, the "Controller" is destroy (I guess it's the way Python works) Here a simple exemple you can run to see the difference:

from  PySide6.QtWidgets import QApplication
import sys

class Test():
    def __init__(self, id):
        self.id = id
        print("TEST " + str(self.id) + " => CREATE")

    def __del__(self):
        print("TEST " + str(self.id) + " => DESTROY")

def main():
    app = QApplication(sys.argv)
    Test(1)
    c = Test(2)
    sys.exit(app.exec_())

if __name__ == '__main__':
    main()

Console output :

TEST 1 => CREATE
TEST 1 => DESTROY
TEST 2 => CREATE