PyQt5 Create QtWidgets.QCheckBox'es on Click Event in runtime

Question

I've got a problem, that i have stumbled across several times. I want to create an arbitrary number of QCheckBoxes on a QPushButton event.

I defined a function wich will be executed by clicking the PushButton. It should make some CheckBoxes, but nothing is shown an the MainWindow. However if I execute the function while creating the MainWindow it works perfectly fine.

I've tried to call the .update(), .repaint() functions in the called function, but nothing happened. I've also tried the janky .hide() .show() fix, but nothing here too. I think I'm missing out on something big.

I include a Minimal example. For keeping things simple I always add two checkboxes, in my project it would depend on the amount of textfiles in a directory. I commented the function call at creating the MainWindow wich would work fine.

minimal Code Example

import sys
from PyQt5 import QtCore
from PyQt5 import QtWidgets

class MainWindow(QtWidgets.QMainWindow):
    def __init__(self,*args,**kwargs):
        super(MainWindow,self).__init__(*args,**kwargs)
        self.c_boxes = []
        
        self.pushButton = QtWidgets.QPushButton( 'HI',self)
        self.pushButton.clicked.connect(self.action)
        #self.action()
        
    def action(self):
        for i in range(2):
            c_box=QtWidgets.QCheckBox(self)
            c_box.move(10,25+ 25*i)
            self.c_boxes.append(c_box)

            
app = QtWidgets.QApplication(sys.argv)
window = MainWindow()
window.show()
app.exec_()