add a progress bar before opening a window

[sof4Rou]

I have a pyqt project where there is a large file processing, when I click on a button (Browse Folder) that will open a window containing treeviews that present the hierarchy of files, the window remains white for a few seconds, so here, I want to display a progress bar (like the loading one), is it possible to do it? if not, please suggest me any other idea.
Here is my code :

class StartWindow(QDialog):
    def __init__(self, parent=None):
        super().__init__(parent)
        self.setWindowTitle('Open ODL File or Folder')
        self.setWindowIcon(QIcon('assets/acls_icon.png'))
        self.setWindowFlags(self.windowFlags() | Qt.WindowMinimizeButtonHint)
        self.resize(600, 400)
    
        main_layout = QHBoxLayout(self)
        buttons_layout = QVBoxLayout()
        self.choose_file_button = QPushButton('Browse File', self)
  
        self.choose_file_button.clicked.connect(self.choose_file)
        buttons_layout.addWidget(self.choose_file_button)
        
        self.choose_folder_button = QPushButton('Browse Folder', self)
   
        self.choose_folder_button.clicked.connect(self.choose_folder)
        buttons_layout.addWidget(self.choose_folder_button)

        main_layout.addLayout(buttons_layout)
        
    def choose_folder(self):
        folder_path = QFileDialog.getExistingDirectory(self, "Open Folder Containing ODL Files")
        if folder_path:
            self.open_folder_view(folder_path)


    def open_folder_view(self, folder_path):
        folder_window = QDialog()
        folder_window.setWindowFlags(self.windowFlags() | Qt.WindowMinimizeButtonHint | Qt.WindowMaximizeButtonHint)
        folder_window.setWindowTitle('ODL Files Tree View')
        folder_window.resize(800, 600)
        folder_window.show()

        processed_files = set() 
        all_groups = set()
        self.folder_path = folder_path
        for root, dirs, files in os.walk(folder_path):
            for filename in files:
                if (filename.endswith(".odl")) and ('acl' in filename.lower() or 'acls' in filename.lower()) and filename not in processed_files:
                    file_path = os.path.join(root, filename)
                    parser = ODLParser(file_path)
                    file_groups, _ = get_headers_and_rights(parser.data_model)
                    all_groups.update(file_groups)
                    tree_view = self.create_tree_view(parser)
                    scroll_layout.addWidget(tree_view)
                    processed_files.add(filename)
                
                elif (filename.endswith(".odl")) and not ('acl' in filename.lower() or 'acls' in filename.lower()) and filename not in processed_files:
                    file_path = os.path.join(root, filename)
                    with open(file_path, 'r', encoding='utf-8') as file:
                        content = file.read()
                        if "acl" in content.lower() and "{" in content.lower():
                            parser = ODLParser2(file_path)
                            file_groups, _ = get_headers_and_rights(parser.data_model)
                            all_groups.update(file_groups)
                            tree_view = self.create_tree_view(parser)
                            scroll_layout.addWidget(tree_view)
                            processed_files.add(filename)
                    
        valid_groups = [group for group in all_groups if group is not None]
        self.group_combobox.addItems(sorted(valid_groups))
        self.group_combobox.setCurrentIndex(0) 
        self.group_combobox.currentTextChanged.connect(self.on_group_combobox_changed)
        QTimer.singleShot(0, lambda: self.on_group_combobox_changed(self.group_combobox.currentText()))
        self.scroll_area.setWidget(scroll_widget)
        layout.addWidget(self.scroll_area)

        folder_window.exec_()

[JonB]

@sof4Rou
See https://doc.qt.io/qtforpython-6/PySide6/QtWidgets/QProgressBar.html and https://doc.qt.io/qtforpython-6/PySide6/QtWidgets/QProgressDialog.html.

You could also probably avoid the "white window"/non-responsive GUI if you split your for root, dirs, files in os.walk(folder_path) and/or for filename in files loop(s) so that it did one/a few elements at a time on a QTimer.