PyQt5 QSlider | Python

Last Updated : 27 Sep, 2019

Slider in PyQt5 is used to set a value with the help of an indicator which can move back and forth over a graphical slide or bar. Many times one needs to provide values which lie between a range and in such cases slider is very useful. QSlider is the class used to add slider in an application.

Example:

A window has a slider and a label(QSlider). The size of the text gets scaled in or out as one move the indicator of the slider.

from PyQt5 import QtCore, QtGui, QtWidgets 
import sys 
  
class Ui_MainWindow(object): 
  
    def setupUi(self, MainWindow): 
  
        MainWindow.resize(550, 393) 
        self.centralwidget = QtWidgets.QWidget(MainWindow) 
        self.centralwidget.setObjectName("centralwidget") 
  
        self.slider = QtWidgets.QSlider(self.centralwidget) 
        self.slider.setGeometry(QtCore.QRect(190, 100, 160, 16)) 
        self.slider.setOrientation(QtCore.Qt.Horizontal) 
  
        # After each value change, slot "scaletext" will get invoked. 
        self.slider.valueChanged.connect(self.scaletext) 
  
        self.label = QtWidgets.QLabel(self.centralwidget) 
        self.label.setGeometry(QtCore.QRect(230, 150, 301, 161)) 
          
        # set initial font size of label. 
        self.font = QtGui.QFont() 
        self.font.setPointSize(7) 
        self.label.setFont(self.font) 
        MainWindow.setCentralWidget(self.centralwidget) 
  
        self.retranslateUi(MainWindow) 
        QtCore.QMetaObject.connectSlotsByName(MainWindow) 
  
    def retranslateUi(self, MainWindow): 
        _translate = QtCore.QCoreApplication.translate 
        MainWindow.setWindowTitle(_translate("MainWindow", "MainWindow")) 
        self.label.setText(_translate("MainWindow", "QSlider")) 
          
    def scaletext(self, value): 
        # Change font size of label. Size value could  
        # be anything consistent with the dimension of label. 
        self.font.setPointSize(7 + value//2) 
        self.label.setFont(self.font) 
      
      
if __name__ == "__main__":  
    app = QtWidgets.QApplication(sys.argv)  
    
    MainWindow = QtWidgets.QMainWindow()  
    ui = Ui_MainWindow()  
    ui.setupUi(MainWindow)  
    MainWindow.show()  
    sys.exit(app.exec_())  