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PyQt5 QScrollBar – Value Changed Signal

  • Last Updated : 03 Aug, 2021

In this article we will see how we can get the value changed signal of QScrollBar. QScrollBar is a control that enables the user to access parts of a document that is larger than the widget used to display it. Slider is the scroll-able object inside the bar. Value is basically depend upon the slider position, scroll bar value changes according to the position of the slider, value increases when slider goes down and decreases when slider moves up. It can be programmatically set with the help of setValue method. This signal is emitted when the scroll bar value get changed.
 

In order to do this we will use valueChanged method with the scroll bar object.
Syntax : scroll.valueChanged.connect(method)
Argument : It takes method as argument
Return : It returns None 
 

Below is the implementation 
 

Python3




# importing libraries
from PyQt5.QtWidgets import *
from PyQt5 import QtCore, QtGui
from PyQt5.QtGui import *
from PyQt5.QtCore import *
import sys
 
 
class Window(QMainWindow):
 
    def __init__(self):
        super().__init__()
 
        # setting title
        self.setWindowTitle("Python ")
 
        # setting geometry
        self.setGeometry(100, 100, 500, 400)
 
        # calling method
        self.UiComponents()
 
        # showing all the widgets
        self.show()
 
 
 
    # method for components
    def UiComponents(self):
 
        scroll = QScrollBar(self)
 
        # setting geometry of the scroll bar
        scroll.setGeometry(100, 50, 30, 200)
 
        # setting value of scroll bar
        scroll.setValue(25)
 
        # making its background color to green
        scroll.setStyleSheet("background : lightgrey;")
 
        # creating a label
        label = QLabel("GeesforGeeks", self)
 
        # setting geometry to the label
        label.setGeometry(200, 100, 300, 80)
 
        # making label multi line
        label.setWordWrap(True)
 
        # getting value changed signal
        scroll.valueChanged.connect(lambda: do_action())
 
        # method called when signal is emitted
        def do_action():
 
            # getting current value
            value = scroll.value()
 
            # setting text to the label
            label.setText("Current Value : " + str(value))
 
 
 
 
# create pyqt5 app
App = QApplication(sys.argv)
 
# create the instance of our Window
window = Window()
 
# start the app
sys.exit(App.exec())

Output : 
 



 

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