[qt5] progress bar - written with camelCase

progress_bar.py

import sys
from PyQt5.QtWidgets import (QWidget, QProgressBar,
                             QPushButton, QApplication)
from PyQt5.QtCore import QBasicTimer


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

    def initUI(self):
        self.progress_bar = QProgressBar(self)
        self.progress_bar.setGeometry(30, 40, 200, 25)

        self.btn = QPushButton('Start', self)
        self.btn.move(30, 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, QTimerEvent):
        if self.step >= 100:
            self.timer.stop()
            self.btn.setText('Finished')
            return
        self.step += 1
        self.progress_bar.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')


if __name__ == "__main__":
    app = QApplication(sys.argv)
    ex = Example()
    sys.exit(app.exec_())