main.py

import sys

from PySide6.QtGui import QGuiApplication
from PySide6.QtQml import QQmlApplicationEngine
from PySide6.QtCore import (
    QTimer,
    Qt,
    QUrl,
    QAbstractListModel,
)

class Model(QAbstractListModel):

    def __init__(self, parent=None):
        QAbstractListModel.__init__(self, parent)
        self.row_count = 200

    def update_model(self, rows):
        self.beginResetModel()
        self.row_count = rows
        self.endResetModel()

    def rowCount(self, parent):
        return self.row_count

    def data(self, index, role=Qt.DisplayRole):
        ix = index.row()
        if ix < self.row_count:
            return "Row {:d}".format(ix)

timer = None
model = Model()

def on_timer_expire():
    model.update_model(0)
    timer.stop()

if __name__ == "__main__":
    app = QGuiApplication(sys.argv)
    engine = QQmlApplicationEngine()

    engine.rootContext().setContextProperty("pythonModel", model)
    engine.load(QUrl("qtbug1.qml"))

    timer = QTimer()
    timer.timeout.connect(on_timer_expire)
    timer.start(3000)  # 3 seconds

    if engine.rootObjects():
        sys.exit(app.exec())
    else:
        sys.exit(1)