QtGui.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 QtGui.QProgressBar widget provides a horizontal or vertical progress bar in PyQt4 toolkit. The programmer can set the minimum and maximum value for the progress bar. The default values are 0 and 99.

#!/usr/bin/python
# -*- coding: utf-8 -*-

"""
ZetCode PyQt4 tutorial 

This example shows a QtGui.QProgressBar widget.

author: Jan Bodnar
website: zetcode.com 
last edited: September 2011
"""

import sys
from PyQt4 import QtGui, QtCore

class Example(QtGui.QWidget):
    
    def __init__(self):
        super(Example, self).__init__()
        
        self.initUI()
        
    def initUI(self):      

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

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

        self.timer = QtCore.QBasicTimer()
        self.step = 0
        
        self.setGeometry(300, 300, 280, 170)
        self.setWindowTitle('QtGui.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 = QtGui.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 = QtGui.QProgressBar(self)

This is a QtGui.QProgressBar constructor.

self.timer = QtCore.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 will 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 QtCore.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.

Figure: QtGui.QProgressBar