ZetCode

PyQt6 widgets

last modified May 3, 2021

Widgets are basic building blocks of an application. PyQt6 has a wide range of various widgets, including buttons, check boxes, sliders, or list boxes. In this section of the tutorial, we describe several useful widgets: a QCheckBox, a QPushButton in tooggle mode, a QSlider, a QProgressBar, and a QCalendarWidget.

PyQt6 QCheckBox

QCheckBox is a widget that has two states: on and off. It is a box with a label. Checkboxes are typically used to represent features in an application that can be enabled or disabled.

check_box.py
#!/usr/bin/python

"""
ZetCode PyQt6 tutorial

In this example, a QCheckBox widget
is used to toggle the title of a window.

Author: Jan Bodnar
Website: zetcode.com
"""

from PyQt6.QtWidgets import QWidget, QCheckBox, QApplication
from PyQt6.QtCore import Qt
import sys


class Example(QWidget):

    def __init__(self):
        super().__init__()

        self.initUI()


    def initUI(self):

        cb = QCheckBox('Show title', self)
        cb.move(20, 20)
        cb.toggle()
        cb.stateChanged.connect(self.changeTitle)

        self.setGeometry(300, 300, 350, 250)
        self.setWindowTitle('QCheckBox')
        self.show()


    def changeTitle(self, state):

        if state == Qt.CheckState.Checked.value:
            self.setWindowTitle('QCheckBox')
        else:
            self.setWindowTitle(' ')


def main():

    app = QApplication(sys.argv)
    ex = Example()
    sys.exit(app.exec())


if __name__ == '__main__':
    main()

We create a checkbox that toggles the window title.

cb = QCheckBox('Show title', self)

This is a QCheckBox constructor.

cb.toggle()

We have set the window title, so we also check the checkbox.

cb.stateChanged.connect(self.changeTitle)

We connect the user defined changeTitle method to the stateChanged signal. The changeTitle method toggles the window title.

if state == Qt.CheckState.Checked.value:
    self.setWindowTitle('QCheckBox')
else:
    self.setWindowTitle(' ')

The state of the widget is given to the changeTitle method in the state variable. If the widget is checked, we set a title of the window. Otherwise, we set an empty string to the titlebar.

QCheckBox
Figure: QCheckBox

Toggle button

A toggle button is a QPushButton in a special mode. It is a button that has two states: pressed and not pressed. We toggle between these two states by clicking on it.

toggle_button.py
#!/usr/bin/python

"""
ZetCode PyQt6 tutorial

In this example, we create three toggle buttons.
They control the background color of a QFrame.

Author: Jan Bodnar
Website: zetcode.com
"""

from PyQt6.QtWidgets import (QWidget, QPushButton,
        QFrame, QApplication)
from PyQt6.QtGui import QColor
import sys


class Example(QWidget):

    def __init__(self):
        super().__init__()

        self.initUI()


    def initUI(self):

        self.col = QColor(0, 0, 0)

        redb = QPushButton('Red', self)
        redb.setCheckable(True)
        redb.move(10, 10)

        redb.clicked[bool].connect(self.setColor)

        greenb = QPushButton('Green', self)
        greenb.setCheckable(True)
        greenb.move(10, 60)

        greenb.clicked[bool].connect(self.setColor)

        blueb = QPushButton('Blue', self)
        blueb.setCheckable(True)
        blueb.move(10, 110)

        blueb.clicked[bool].connect(self.setColor)

        self.square = QFrame(self)
        self.square.setGeometry(150, 20, 100, 100)
        self.square.setStyleSheet("QWidget { background-color: %s }" %
                                  self.col.name())

        self.setGeometry(300, 300, 300, 250)
        self.setWindowTitle('Toggle button')
        self.show()


    def setColor(self, pressed):

        source = self.sender()

        if pressed:
            val = 255
        else:
            val = 0

        if source.text() == "Red":
            self.col.setRed(val)
        elif source.text() == "Green":
            self.col.setGreen(val)
        else:
            self.col.setBlue(val)

        self.square.setStyleSheet("QFrame { background-color: %s }" %
                                  self.col.name())


def main():

    app = QApplication(sys.argv)
    ex = Example()
    sys.exit(app.exec())


if __name__ == '__main__':
    main()

In our example, we create three toggle buttons and a QWidget. We set the background colour of the QWidget to black. The toggle buttons toggle the red, green, and blue parts of the colour value. The background colour depends on which toggle buttons is pressed.

self.col = QColor(0, 0, 0)

This is the initial, black colour value.

redb = QPushButton('Red', self)
redb.setCheckable(True)
redb.move(10, 10)

To create a toggle button, we create a QPushButton and make it checkable by calling the setCheckable method.

redb.clicked[bool].connect(self.setColor)

We connect a clicked signal to our user defined method. We use the clicked signal that operates with a Boolean value.

source = self.sender()

We get the button which was toggled.

if source.text() == "Red":
    self.col.setRed(val)

In case it is a red button, we update the red part of the colour accordingly.

self.square.setStyleSheet("QFrame { background-color: %s }" %
    self.col.name())

We use style sheets to change the background colour. The stylesheet is updated with setStyleSheet method.

Toggle button
Figure: Toggle button

PyQt6 QSlider

A QSlider is a widget that has a simple handle. This handle can be pulled back and forth. This way we are choosing a value for a specific task. Sometimes using a slider is more natural than entering a number or using a spin box.

In our example we show one slider and one label. The label displays an image. The slider controls the label.

slider.py
#!/usr/bin/python

"""
ZetCode PyQt6 tutorial

This example shows a QSlider widget.

Author: Jan Bodnar
Website: zetcode.com
"""

from PyQt6.QtWidgets import (QWidget, QSlider,
        QLabel, QApplication)
from PyQt6.QtCore import Qt
from PyQt6.QtGui import QPixmap
import sys


class Example(QWidget):

    def __init__(self):
        super().__init__()

        self.initUI()


    def initUI(self):

        sld = QSlider(Qt.Orientation.Horizontal, self)
        sld.setFocusPolicy(Qt.FocusPolicy.NoFocus)
        sld.setGeometry(30, 40, 200, 30)
        sld.valueChanged[int].connect(self.changeValue)

        self.label = QLabel(self)
        self.label.setPixmap(QPixmap('mute.png'))
        self.label.setGeometry(250, 40, 80, 30)

        self.setGeometry(300, 300, 350, 250)
        self.setWindowTitle('QSlider')
        self.show()


    def changeValue(self, value):

        if value == 0:

            self.label.setPixmap(QPixmap('mute.png'))
        elif 0 < value <= 30:

            self.label.setPixmap(QPixmap('min.png'))
        elif 30 < value < 80:

            self.label.setPixmap(QPixmap('med.png'))
        else:

            self.label.setPixmap(QPixmap('max.png'))


def main():

    app = QApplication(sys.argv)
    ex = Example()
    sys.exit(app.exec())


if __name__ == '__main__':
    main()

In our example we simulate a volume control. By dragging the handle of a slider, we change an image on the label.

sld = QSlider(Qt.Orientation.Horizontal, self)

Here we create a horizontal QSlider.

self.label = QLabel(self)
self.label.setPixmap(QPixmap('mute.png'))

We create a QLabel widget and set an initial mute image to it.

sld.valueChanged[int].connect(self.changeValue)

We connect the valueChanged signal to the user defined changeValue method.

if value == 0:
    self.label.setPixmap(QPixmap('mute.png'))
...

Based on the value of the slider, we set an image to the label. In the above code, we set the mute.png image to the label if the slider is equal to zero.

QSlider widget
Figure: QSlider widget

PyQt6 QProgressBar

A progress bar is a widget that is used when we process lengthy tasks. It is animated so that the user knows that the task is progressing. The QProgressBar widget provides a horizontal or a vertical progress bar in PyQt6 toolkit. The programmer can set the minimum and maximum value for the progress bar. The default values are 0 and 99.

progressbar.py
#!/usr/bin/python

"""
ZetCode PyQt6 tutorial

This example shows a QProgressBar widget.

Author: Jan Bodnar
Website: zetcode.com
"""

from PyQt6.QtWidgets import (QWidget, QProgressBar,
        QPushButton, QApplication)
from PyQt6.QtCore import QBasicTimer
import sys


class Example(QWidget):

    def __init__(self):
        super().__init__()

        self.initUI()


    def initUI(self):

        self.pbar = QProgressBar(self)
        self.pbar.setGeometry(30, 40, 200, 25)

        self.btn = QPushButton('Start', self)
        self.btn.move(40, 80)
        self.btn.clicked.connect(self.doAction)

        self.timer = QBasicTimer()
        self.step = 0

        self.setGeometry(300, 300, 280, 170)
        self.setWindowTitle('QProgressBar')
        self.show()


    def timerEvent(self, e):

        if self.step >= 100:

            self.timer.stop()
            self.btn.setText('Finished')
            return

        self.step = self.step + 1
        self.pbar.setValue(self.step)


    def doAction(self):

        if self.timer.isActive():
            self.timer.stop()
            self.btn.setText('Start')
        else:
            self.timer.start(100, self)
            self.btn.setText('Stop')


def main():

    app = QApplication(sys.argv)
    ex = Example()
    sys.exit(app.exec())


if __name__ == '__main__':
    main()

In our example we have a horizontal progress bar and a push button. The push button starts and stops the progress bar.

self.pbar = QProgressBar(self)

This is a QProgressBar constructor.

self.timer = QBasicTimer()

To activate the progress bar, we use a timer object.

self.timer.start(100, self)

To launch a timer event, we call its start method. This method has two parameters: the timeout and the object which receive the events.

def timerEvent(self, e):

    if self.step >= 100:

        self.timer.stop()
        self.btn.setText('Finished')
        return

    self.step = self.step + 1
    self.pbar.setValue(self.step)

Each QObject and its descendants have a timerEvent event handler. In order to react to timer events, we reimplement the event handler.

def doAction(self):

    if self.timer.isActive():
        self.timer.stop()
        self.btn.setText('Start')

    else:
        self.timer.start(100, self)
        self.btn.setText('Stop')

Inside the doAction method, we start and stop the timer.

QProgressBar
Figure: QProgressBar

PyQt6 QCalendarWidget

A QCalendarWidget provides a monthly based calendar widget. It allows a user to select a date in a simple and intuitive way.

calendar.py
#!/usr/bin/python

"""
ZetCode PyQt6 tutorial

This example shows a QCalendarWidget widget.

Author: Jan Bodnar
Website: zetcode.com
"""

from PyQt6.QtWidgets import (QWidget, QCalendarWidget,
        QLabel, QApplication, QVBoxLayout)
from PyQt6.QtCore import QDate
import sys


class Example(QWidget):

    def __init__(self):
        super().__init__()

        self.initUI()


    def initUI(self):

        vbox = QVBoxLayout(self)

        cal = QCalendarWidget(self)
        cal.setGridVisible(True)
        cal.clicked[QDate].connect(self.showDate)

        vbox.addWidget(cal)

        self.lbl = QLabel(self)
        date = cal.selectedDate()
        self.lbl.setText(date.toString())

        vbox.addWidget(self.lbl)

        self.setLayout(vbox)

        self.setGeometry(300, 300, 350, 300)
        self.setWindowTitle('Calendar')
        self.show()


    def showDate(self, date):
        self.lbl.setText(date.toString())


def main():

    app = QApplication(sys.argv)
    ex = Example()
    sys.exit(app.exec())


if __name__ == '__main__':
    main()

The example has a calendar widget and a label widget. The currently selected date is displayed in the label widget.

cal = QCalendarWidget(self)

The QCalendarWidget is created.

cal.clicked[QDate].connect(self.showDate)

If we select a date from the widget, a clicked[QDate] signal is emitted. We connect this signal to the user defined showDate method.

def showDate(self, date):

    self.lbl.setText(date.toString())

We retrieve the selected date by calling the selectedDate method. Then we transform the date object into string and set it to the label widget.

In this part of the PyQt6 tutorial, we have covered the following widgets: QCheckBox, QPushButton in tooggle mode, QSlider, QProgressBar, and QCalendarWidget.