[FIXED] How to show PySide/PyQt UI and auto-run one of its methods?

Issue

I wish to open a PySide/PyQt window and automatically start executing a method, which will show a progress in the UI while it is executing.

With the code below, the ui is not shown until the process has completed, thus you cannot see the progress. How can I change the code to see the progress before the process has completed?

from PySide import QtGui
import time

class MyApp(QtGui.QMainWindow)
    def __init__(self, parent=None):
        super(MyApp, self).__init__(parent)

        # Setup
        self.centralWidget = QtGui.QWidget(self)
        self.setCentralWidget(self.centralWidget)
        self.setup_UI()

        # Execute process!
        self.process()

    def setup_UI(self):
        ''' Attach widgets to window '''
        self.mainLayout=QtGui.QVBoxLayout(self.centralWidget)
        self.list_widget = QtGui.QListWidget()
        self.progress_bar = QtGui.QProgressBar()
        self.mainLayout.addWidget(self.list_widget)
        self.mainLayout.addWidget(self.progress_bar)

    def process(self):
        ''' Manipulate the ui '''
        self.progress_bar.setMaximum(0)
        self.progress_bar.setMaximum(10)

        for x in range(0, 10):
            time.sleep(1)
            self.list_widget.addItem('Item ' + str(x))
            self.progress_bar.setValue(x)



my_app = MyApp()
my_app.show()

Solution

Your main problem that you are blocking qt main thread by calling time.sleep. To solve this issue you have two options. One of them is using threading. Another option is change your code to asynchronous like this:

from PySide import QtGui, QtCore
import time
import sys

class MyApp(QtGui.QMainWindow):
    def __init__(self, parent=None):
        super(MyApp, self).__init__(parent)

        # Setup
        self.centralWidget = QtGui.QWidget(self)
        self.setCentralWidget(self.centralWidget)
        self.setup_UI()

        # Execute process!
        self.set_process()
        self.timer = QtCore.QTimer()
        self.i = 0
        self.timer.timeout.connect(self.update)
        self.timer.start(1000)

    def setup_UI(self):
        ''' Attach widgets to window '''
        self.mainLayout=QtGui.QVBoxLayout(self.centralWidget)
        self.list_widget = QtGui.QListWidget()
        self.progress_bar = QtGui.QProgressBar()
        self.mainLayout.addWidget(self.list_widget)
        self.mainLayout.addWidget(self.progress_bar)

    def set_process(self):
        ''' Manipulate the ui '''
        self.progress_bar.setMaximum(0)
        self.progress_bar.setMaximum(10)

    def update(self):
        if self.i > 9:
            self.timer.stop()

        self.list_widget.addItem('Item ' + str(self.i))
        self.progress_bar.setValue(self.i)
        self.i += 1


def main():
    app = QtGui.QApplication(sys.argv)
    my_win = MyApp()
    my_win.show()
    sys.exit(app.exec_())


if __name__ == "__main__":
    main()

This example are using Qtimer object for updating progress bar with delay.

Answered By - Slava Bacherikov