Python custom progress bar widget with PyQt

Python PyQt Widgets: Exercise-12 with Solution

Write a Python program to create a custom progress bar widget that displays a progress percentage using PyQt. Create methods to set and update progress values.

From doc.qt.io:

QApplication Class: The QApplication class manages the GUI application's control flow and main settings.

QWidget Class: The QWidget class is the base class of all user interface objects.

QVBoxLayout Class: The QVBoxLayout class lines up widgets vertically.

QPushButton Class: The QPushButton widget provides a command button.

QPainter Class: The QPainter class performs low-level painting on widgets and other paint devices.

QColor Class: The QColor class provides colors based on RGB, HSV or CMYK values.

QFont Class: The QFont class specifies a query for a font used for drawing text.

Sample Solution:

Python Code:

import sys
from PyQt5.QtWidgets import QApplication, QWidget, QVBoxLayout, QPushButton
from PyQt5.QtGui import QPainter, QColor, QFont
from PyQt5.QtCore import Qt, QTimer

class CustomProgressBar(QWidget):
    def __init__(self):
        super().__init__()
        self.setMinimumSize(300, 50)
        self.progress = 0

    def set_progress(self, value):
        self.progress = value
        self.update()

    def paintEvent(self, event):
        painter = QPainter(self)
        painter.setRenderHint(QPainter.Antialiasing)

        # Define progress bar dimensions
        bar_width = 250
        bar_height = 30
        bar_x = (self.width() - bar_width) / 2
        bar_y = (self.height() - bar_height) / 2

        # Draw the background of the progress bar
        painter.setPen(Qt.NoPen)
        painter.setBrush(QColor(200, 200, 200))
        painter.drawRect(bar_x, bar_y, bar_width, bar_height)

        # Draw the filled portion of the progress bar
        fill_width = int(bar_width * (self.progress / 100))
        painter.setBrush(QColor(0, 160, 230))
        painter.drawRect(bar_x, bar_y, fill_width, bar_height)

        # Display progress percentage text
        font = QFont("Arial", 12)
        painter.setFont(font)
        painter.setPen(QColor(0, 0, 0))
        text = f"{int(self.progress)}%"
        text_width = painter.fontMetrics().width(text)
        text_x = (self.width() - text_width) / 2
        text_y = bar_y + bar_height + 20
        painter.drawText(text_x, text_y, text)

class ProgressBarApp(QWidget):
    def __init__(self):
        super().__init__()
        self.setWindowTitle("Custom Progress Bar")
        self.setGeometry(100, 100, 400, 200)

        layout = QVBoxLayout()
        self.progress_bar = CustomProgressBar()
        layout.addWidget(self.progress_bar)

        self.button = QPushButton("Start Progress")
        self.button.clicked.connect(self.start_progress)
        layout.addWidget(self.button)

        self.setLayout(layout)

        # Initialize timer for smooth progress update
        self.timer = QTimer(self)
        self.timer.timeout.connect(self.update_progress)

    def start_progress(self):
        self.progress = 0
        self.button.setEnabled(False)
        self.timer.start(100)  # Update every 100 milliseconds

    def update_progress(self):
        if self.progress <= 100:
            self.progress_bar.set_progress(self.progress)
            self.progress += 1
        else:
            self.timer.stop()
            self.button.setEnabled(True)

def main():
    app = QApplication(sys.argv)
    window = ProgressBarApp()
    window.show()
    sys.exit(app.exec_())

if __name__ == "__main__":
    main()

Explanation:

In the exercise above -

• Import the necessary modules from PyQt5.
• Create a CustomProgressBar class that subclasses QWidget to create the custom progress bar widget.
• The "set_progress()" method allows you to set the progress value and triggers a repaint of the progress bar.
• In the "paintEvent()" method, we use QPainter to draw the progress bar and the filled portion based on the progress value.
• Display the progress percentage text below the progress bar.
• The "ProgressBarApp" class creates the main application window with a custom progress bar and a button to start progress updates.
• Added a QTimer named timer to the ProgressBarApp class. This timer periodically calls the "update_progress()" method.
• The "start_progress()" initializes the progress value and starts the timer to update the progress every 100 milliseconds.
• It is disabled during progress updates and enabled after completion.

Output:

Flowchart:

Python Code Editor:

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