[PyQt] addLayout() / setLayout() 쓰임

- container
QGroupBox() / QWidget() / QScrollArea() / QToolBox() / QTabWidget() / QStackedWidget() / QFrame() / QMdiArea() / QDockWIdget()
    setLayout()

    addWidget()

- layout
QBoxLayout() / QGridLayout() / QFormLayout()
    addLayout()
    addWidget()

for idx in range(self.layout().count()):
    item = self.layout().itemAt(idx).widget()
    item.setCheckState(Qt.Unchecked)


while not self.layout().isEmpty():
    item = self.layout().itemAt(0).widget()
    # item.setVisible(False)
    self.layout().removeWidget(item)
    del item


while not self.layout().count() > 0:
    child = self.layout().itemAt(0)
    item = child.widget()

    if item:
        item.deleteLater()