PyQt Basic Widgets PyQt QSlider Widget & Signal - PyQt

What is PyQt QSlider Widget & Signal?

QSlider class object presents the user with a groove over which a manage may be moved. it is a classic widget to control a bounded cost. role of the manage at the groove is equal to an integer between the decrease and the higher bounds of the manage.

A slider manage may be displayed in horizontal or vertical manner by using mentioning the orientation in the constructor.

self.sp = QSlider(Qt.Horizontal) self.sp = QSlider(Qt.Vertical)

The following table lists some of the frequently used methods of QSlider class −

Given below are the most commonly used methods of QSlider.

QSlider Signals

valueChanged() signal is the one which is most frequently used.

Example

The following example demonstrates the above functionality. A Label and a horizontal slider is placed in a vertical format. Slider’s valueChanged() signal is attached to valuechange() technique.

self.sl.valueChanged.connect(self.valuechange)

The slot feature valuechange() reads current value of the slider and makes use of it as the size of font for label’s caption.

size = self.sl.value() self.l1.setFont(QFont("Arial",size))

The complete code is as follows −

import sys from PyQt4.QtCore import * from PyQt4.QtGui import * class sliderdemo(QWidget): def __init__(self, parent = None): super(sliderdemo, self).__init__(parent) layout = QVBoxLayout() self.l1 = QLabel("Hello") self.l1.setAlignment(Qt.AlignCenter) layout.addWidget(self.l1) self.sl = QSlider(Qt.Horizontal) self.sl.setMinimum(10) self.sl.setMaximum(30) self.sl.setValue(20) self.sl.setTickPosition(QSlider.TicksBelow) self.sl.setTickInterval(5) layout.addWidget(self.sl) self.sl.valueChanged.connect(self.valuechange) self.setLayout(layout) self.setWindowTitle("SpinBox demo") def valuechange(self): size = self.sl.value() self.l1.setFont(QFont("Arial",size)) def main(): app = QApplication(sys.argv) ex = sliderdemo() ex.show() sys.exit(app.exec_()) if __name__ == '__main__': main()

The above code produces the following output −

The font length of the label changes as handle of the slider is moved across the handle.