{"id":4984,"date":"2022-09-21T01:00:02","date_gmt":"2022-09-21T01:00:02","guid":{"rendered":"https:\/\/www.pythontutorial.net\/?page_id=4984"},"modified":"2022-10-29T07:49:43","modified_gmt":"2022-10-29T07:49:43","slug":"pyqt-qcheckbox","status":"publish","type":"page","link":"https:\/\/www.pythontutorial.net\/pyqt\/pyqt-qcheckbox\/","title":{"rendered":"PyQt QCheckBox"},"content":{"rendered":"\n

Summary<\/strong>: in this tutorial, you’ll learn how to use the PyQt QCheckBox<\/code> class to create a checkbox widget.<\/p>\n\n\n\n

Introduction to the PyQt QCheckBox widget #<\/a><\/h2>\n\n\n\n

The QCheckBox<\/code> class allows you to create a checkbox widget, which can be switched on or off. To create a checkbox using the QCheckBox<\/code> class, you follow these steps:<\/p>\n\n\n\n

First, import the QCheckBox<\/code> class:<\/p>\n\n\n

from<\/span> PyQt6.QtWidgets import<\/span> QCheckBox<\/code><\/span>Code language:<\/span> JavaScript<\/span> (<\/span>javascript<\/span>)<\/span><\/small><\/pre>\n\n\n
Second, create a new instance of the QCheckBox<\/code> class:<\/p>\n\n\n
checkbox = QCheckBox(text)<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
The following program shows a window that has a checkbox:<\/p>\n\n\n
import<\/span> sys\nfrom<\/span> PyQt6.QtWidgets import<\/span> QApplication, QWidget, QCheckBox, QGridLayout\nfrom<\/span> PyQt6.QtCore import<\/span> Qt\n\n\nclass<\/span> MainWindow<\/span>(QWidget)<\/span>:<\/span>\n    def<\/span> __init__<\/span>(self, *args, **kwargs)<\/span>:<\/span>\n        super().__init__(*args, **kwargs)\n\n        self.setWindowTitle('PyQt QCheckBox'<\/span>)\n        self.setGeometry(100<\/span>, 100<\/span>, 320<\/span>, 210<\/span>)\n\n        # create a grid layout<\/span>\n        layout = QGridLayout()\n        self.setLayout(layout)\n\n        # create a checkbox<\/span>\n        checkbox = QCheckBox('I agree'<\/span>, self)\n\n        layout.addWidget(checkbox, 0<\/span>, 0<\/span>, Qt.AlignmentFlag.AlignCenter)\n\n        # show the window<\/span>\n        self.show()\n\n\nif<\/span> __name__ == '__main__'<\/span>:\n    app = QApplication(sys.argv)\n    window = MainWindow()\n    sys.exit(app.exec())<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n\n
\"\"<\/figure>\n\n\n\n
The stateChanged signal #<\/a><\/h2>\n\n\n\n
A checkbox emits the stateChanged<\/code> signal whenever you check or uncheck it. <\/p>\n\n\n\n
If you want to do something when the checkbox is checked or unchecked, you can connect a slot to the stateChanged<\/code> signal. For example:<\/p>\n\n\n
checkbox = QCheckBox('I agree'<\/span>, self)\ncheckbox.stateChanged.connect(self.on_checkbox_changed)<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
The stateChanged<\/code> signal sends a value that indicates whether the button is checked or unchecked. To check the state of a QCheckBox<\/code>, you create a Qt.CheckState<\/code> instance:<\/p>\n\n\n
state = Qt.CheckState(value)<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
And compare it with one of three values:<\/p>\n\n\n\n
State<\/th>Meaning<\/th><\/tr><\/thead>
Qt.CheckState.Checked<\/code><\/td>Checked<\/td><\/tr>
Qt.CheckState.Unchecked<\/code><\/td>Unchecked<\/td><\/tr>
Qt.CheckState.PartiallyChecked<\/code><\/td>Partially checked<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
Note that the Qt.CheckState.PartiallyChecked<\/code> is used for a tristate checkbox that will be covered shortly.<\/p>\n\n\n\n
For example:<\/p>\n\n\n
def<\/span> on_checkbox_changed<\/span>(self, value)<\/span>:<\/span>\n    state = Qt.CheckState(value)\n    if<\/span> state == Qt.CheckState.Checked:\n        print('Checked'<\/span>)\n    elif<\/span> state == Qt.CheckState.Unchecked:\n        print('Unchecked'<\/span>)<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Also, you can use the isChecked()<\/code> method to check if a checkbox is checked.<\/p>\n\n\n\n
The following shows a complete program that displays a message in the console when a checkbox is checked or unchecked:<\/p>\n\n\n
import<\/span> sys\nfrom<\/span> PyQt6.QtWidgets import<\/span> QApplication, QWidget, QCheckBox, QGridLayout\nfrom<\/span> PyQt6.QtCore import<\/span> Qt\n\n\nclass<\/span> MainWindow<\/span>(QWidget)<\/span>:<\/span>\n    def<\/span> __init__<\/span>(self, *args, **kwargs)<\/span>:<\/span>\n        super().__init__(*args, **kwargs)\n\n        self.setWindowTitle('PyQt QCheckBox'<\/span>)\n        self.setGeometry(100<\/span>, 100<\/span>, 320<\/span>, 210<\/span>)\n\n        # create a grid layout<\/span>\n        layout = QGridLayout()\n        self.setLayout(layout)\n\n        # create a checkbox<\/span>\n        checkbox = QCheckBox('I agree'<\/span>, self)\n        checkbox.stateChanged.connect(self.on_checkbox_changed)\n\n        layout.addWidget(checkbox, 0<\/span>, 0<\/span>, Qt.AlignmentFlag.AlignCenter)\n\n        # show the window<\/span>\n        self.show()\n\n    def<\/span> on_checkbox_changed<\/span>(self, value)<\/span>:<\/span>\n        state = Qt.CheckState(value)\n        if<\/span> state == Qt.CheckState.Checked:\n            print('Checked'<\/span>)\n        elif<\/span> state == Qt.CheckState.Unchecked:\n            print('Unchecked'<\/span>)\n\n\nif<\/span> __name__ == '__main__'<\/span>:\n    app = QApplication(sys.argv)\n    window = MainWindow()\n    sys.exit(app.exec())<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Setting checked or unchecked of PyQt QCheckBox programmatically #<\/a><\/h2>\n\n\n\n
The QCheckBox<\/code> class has the setChecked()<\/code> method that allows you to check or uncheck a checkbox programmatically.<\/p>\n\n\n\n
If you pass True<\/code> to the setChecked()<\/code> method, the checkbox will be checked. However, if you pass False<\/code> to the setCheck()<\/code> method, the checkbox will be unchecked.<\/p>\n\n\n\n
Also, you can use the setCheckState()<\/code> method of the QCheckBox<\/code> class to set the state of the checkbox. The setCheckState()<\/code> method accepts one of three state values of the Qt.CheckState<\/code> enum.<\/p>\n\n\n\n
The following program illustrates how to use the setChecked()<\/code> method to check and uncheck a checkbox:<\/p>\n\n\n
import<\/span> sys\nfrom<\/span> PyQt6.QtWidgets import<\/span> QApplication, QWidget, QCheckBox, QPushButton, QGridLayout\nfrom<\/span> PyQt6.QtCore import<\/span> Qt\n\n\nclass<\/span> MainWindow<\/span>(QWidget)<\/span>:<\/span>\n    def<\/span> __init__<\/span>(self, *args, **kwargs)<\/span>:<\/span>\n        super().__init__(*args, **kwargs)\n\n        self.setWindowTitle('PyQt QCheckBox'<\/span>)\n        self.setGeometry(100<\/span>, 100<\/span>, 320<\/span>, 210<\/span>)\n\n        # create a grid layout<\/span>\n        layout = QGridLayout()\n        self.setLayout(layout)\n\n        # create a checkbox<\/span>\n        self.checkbox = QCheckBox('I agree'<\/span>, self)\n\n        check_button = QPushButton('Check'<\/span>, self)\n        check_button.clicked.connect(self.check)\n\n        uncheck_button = QPushButton('Uncheck'<\/span>, self)\n        uncheck_button.clicked.connect(self.uncheck)\n\n        layout.addWidget(self.checkbox, 0<\/span>, 0<\/span>, 0<\/span>, 2<\/span>,\n                         Qt.AlignmentFlag.AlignCenter)\n        layout.addWidget(check_button, 1<\/span>, 0<\/span>)\n        layout.addWidget(uncheck_button, 1<\/span>, 1<\/span>)\n\n        # show the window<\/span>\n        self.show()\n\n    def<\/span> check<\/span>(self)<\/span>:<\/span>\n        self.checkbox.setChecked(True<\/span>)\n\n    def<\/span> uncheck<\/span>(self)<\/span>:<\/span>\n        self.checkbox.setChecked(False<\/span>)\n\n\nif<\/span> __name__ == '__main__'<\/span>:\n    app = QApplication(sys.argv)\n    window = MainWindow()\n    sys.exit(app.exec())<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n\n
\"\"<\/figure>\n\n\n\n
How it works.<\/p>\n\n\n\n
First, create a checkbox and add it to the attribute of the class:<\/p>\n\n\n
self.checkbox = QCheckBox('I agree'<\/span>, self)<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
By making the checkbox an attribute of the class, we can reference it in other methods within the same class.<\/p>\n\n\n\n
check_button = QPushButton('Check'<\/span>, self)\ncheck_button.clicked.connect(self.check)\n\nuncheck_button = QPushButton('Uncheck'<\/span>, self)\nuncheck_button.clicked.connect(self.uncheck)<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Third, call the setChecked()<\/code> method with True to check the checkbox in the check()<\/code> method:<\/p>\n\n\n
def<\/span> check<\/span>(self)<\/span>:<\/span>\n    self.checkbox.setChecked(True<\/span>)<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Finally, call the setChecked()<\/code> method with False to uncheck the checkbox in the uncheck()<\/code> method:<\/p>\n\n\n
def<\/span> uncheck<\/span>(self)<\/span>:<\/span>\n    self.checkbox.setChecked(False<\/span>)<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Creating a tristate checkbox #<\/a><\/h2>\n\n\n\n
Besides checked and unchecked, a QCheckBox<\/code> supports the third state that indicates “no change”. In this case, a checkbox has three states: <\/p>\n\n\n\n
Second, create two QPushButton<\/a><\/code> widgets and connect each of them to the check()<\/code> and uncheck()<\/code> methods:<\/p>\n\n\n
Note that the program uses the QGridLayout<\/a><\/code> to place the check box on the window.<\/p>\n\n\n\n