PySide6 QCheckBox stateChanged() generates state event int instead of Qt.CheckState

[Erriez]

PySide6 6.4.1 PIP on Ubuntu and Windows contains a QCheckBox with stateChanged() API call to generate an event when the checkbox state changes.

• QCheckBox documentation:
  • state contains the checkbox’s new CheckState.
• PySide6.QtCore.Qt.CheckState documentation:
  • This enum describes the state...
  • Qt.Checked: The item is checked..

The QCheckBox generated event argument state is type int instead of enum CheckState:

Testcase below demonstrates not working checkbox event state:

from PySide6.QtWidgets import QApplication, QWidget, QCheckBox
from PySide6.QtCore import Qt
import sys

class Window(QWidget):
    def __init__(self):
        super().__init__()

        self.setGeometry(300, 300, 250, 150)
        self.setWindowTitle('QCheckBox')

        checkbox = QCheckBox('Show title', self)
        checkbox.move(20, 20)
        checkbox.toggle()
        checkbox.setTristate(True)
        checkbox.stateChanged.connect(self.onCheckboxChange)

    def onCheckboxChange(self, state):
        # state = int and not Qt.Checked or Qt.Unchecked
        # This is not matching with the documentation

        print('Qt.Checked type: {}'.format(type(Qt.Checked)))
        print('Event: {}, type: {}'.format(state, type(state)))

        # Always setting title to UNKNOWN as this is an incorrect type comparison
        if state == Qt.Unchecked:
            self.setWindowTitle('Unchecked')
        elif state == Qt.PartiallyChecked:
            self.setWindowTitle('PartiallyChecked')
        elif state == Qt.Checked:
            self.setWindowTitle('Checked')
        else:
            self.setWindowTitle('UNKNOWN')

def main():
    app = QApplication(sys.argv)
    window = Window()
    window.show()
    sys.exit(app.exec())

if __name__ == '__main__':
    main()

Output:

# When unchecking checkbox:
Qt.Checked type: <enum 'CheckState'>
Event: 0, type: <class 'int'>    <= Expected Qt.Unchecked:

# When partially checking checkbox:
Qt.Checked type: <enum 'CheckState'>
Event: 1, type: <class 'int'>    <= Expected Qt.PartiallyChecked:

# When checking checkbox:
Qt.Checked type: <enum 'CheckState'>
Event: 2, type: <class 'int'>    <= Expected Qt.Checked:

I don't know how to convert the Qt.Checked , Qt.PartiallyChecked or Qt.Unchecked to an int.
Casting with if state == int(Qt.Checked) generates:

• TypeError: int() argument must be a string, a bytes-like object or a real number, not 'CheckState'

Is this expected behavior?

[friedemannkleint]

Qt.Checked.value can be used to obtain the int value of the Enum-derived class.

[JonB]

@Erriez said in PySide6 QCheckBox stateChanged() generates state event int instead of Qt.CheckState:

Casting with if state == int(Qt.Checked) generates:
Is this expected behavior?

Apparently so! Have a read of https://stackoverflow.com/questions/72161415/qt-checkstate-checked-2-and-qt-checkstate-checked-0. You are supposed to do the "cast" the other way round, not from enum to int but from int to the enum:

if Qt.CheckState(state) == Qt.CheckState.Unchecked

etc. Or you can make your if ... elif ... code neater with:

state = Qt.CheckState(state)
if state == Qt.CheckState.Unchecked;
elif state == Qt.CheckState.PartiallyChecked:
elif state == Qt.CheckState.Checked:

You can indeed also use @friedemannkleint's state == Qt.CheckState.Unchecked.value

[Erriez]

@JonB Thanks for your explanation. I confirm that both state = Qt.CheckState(state) and state == Qt.CheckState.Unchecked.value works which answered my question.

And the reason is that we as beginner start with an incorrect example.

[JonB]

@Erriez
That example has

from PySide import

which looks awfully like PySide 1 to me, from yonks ago! I think the behaviour you are asking about would have first appeared in PySide6, when they "tightened" handling of enumerated types...?

[friedemannkleint]

Our examples gallery: https://doc.qt.io/qtforpython-6/examples/index.html

[Erriez]

Thanks for pointing to the (advanced) examples. That's the right way to go.