Python: QtGui.QProgressBar Color

Question

I'm wondering if there is a way to customize a color of the progress bar (QtGui.QProgressBar). Let's say we would want to make it green when bar reaches 100%.

Here is a working example:

import sys, time
from PyQt4 import QtCore, QtGui

class PbWidget(QtGui.QProgressBar):
    def __init__(self, parent=None, total=20):
        super(PbWidget, self).__init__()
        self.setMinimum(1)
        self.setMaximum(total)        
        self._active = False  

    def update_bar(self, to_add_number):
        while True:
            time.sleep(0.01)
            value = self.value() + to_add_number            
            self.setValue(value)
            QtGui.qApp.processEvents()
            if (not self._active or value >= self.maximum()):                
                break
        self._active = False

    def closeEvent(self, event):
        self._active = False


class MainWindow(QtGui.QMainWindow):
    def __init__(self):
        super(MainWindow, self).__init__()
        self.main_layout = QtGui.QVBoxLayout()

        self.pb=PbWidget(total=101)
        self.main_layout.addWidget(self.pb)

        ok_button = QtGui.QPushButton("Press to update Progress Bar")
        ok_button.clicked.connect(self.OK)      
        self.main_layout.addWidget(ok_button)       

        central_widget = QtGui.QWidget()
        central_widget.setLayout(self.main_layout)
        self.setCentralWidget(central_widget)

    def OK(self):
        self.pb.update_bar(10)

if __name__ == '__main__':
    import sys
    app = QtGui.QApplication(sys.argv)
    window = MainWindow()
    window.resize(480, 320)
    window.show()
    sys.exit(app.exec_())

Answer 1

Yes, use CSS for that. Yes CSS you have readed well! ;)

add this function to your PbWidget class:

def change_color(self, color):
    template_css = """QProgressBar::chunk { background: %s; }"""
    css = template_css % color
    self.setStyleSheet(css)

the color parameter expects something like: "yellow", "blue", "red" ... and also HEX notation: "#FFD45", etc ...

You can call this function inside update_bar and pass to it some color depending on the progress bar value. For example:

def update_bar(self, to_add_number):
    while True:
        time.sleep(0.5)
        value = self.value() + to_add_number            
        self.setValue(value)
        if value > 50:
            self.change_color("yellow")
        QtGui.qApp.processEvents()
        if (value >= self.maximum()):                
            break
    self._active = False

For changing others visual properties, visit: Qt StyleSheet Reference and look for QtProgressBar. Good luck!!!