PyQt5 Dynamically add rectangles to QML grid

main.py

from PyQt5.QtGui import QGuiApplication, QColor
from PyQt5.QtQml import QQmlApplicationEngine, QQmlComponent
from PyQt5.QtCore import QUrl, Qt, QCoreApplication, QAbstractListModel, QModelIndex, QTimer, qsrand, qrand, QTime
from PyQt5.QtQuick import QQuickItem

class Data(object):
    def __init__(self, width=35, height=35, color=QColor("red")):
        self._width = width
        self._height = height
        self._color = color

    def width(self):
        return self._width

    def height(self):
        return self._height

    def color(self):
        return self._color

class Model(QAbstractListModel):

    WidthRole = Qt.UserRole + 1
    HeightRole = Qt.UserRole + 2
    ColorRole = Qt.UserRole + 3

    _roles = {WidthRole: b"width", HeightRole: b"height", ColorRole: b"color"}

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

        self._datas = []

    def addData(self, data):
        self.beginInsertRows(QModelIndex(), self.rowCount(), self.rowCount())
        self._datas.append(data)
        self.endInsertRows()

    def rowCount(self, parent=QModelIndex()):
        return len(self._datas)

    def data(self, index, role=Qt.DisplayRole):
        try:
            data = self._datas[index.row()]
        except IndexError:
            return QVariant()

        if role == self.WidthRole:
            return data.width()

        if role == self.HeightRole:
            return data.height()

        if role == self.ColorRole:
            return data.color()

        return QVariant()

    def roleNames(self):
        return self._roles


if __name__ == "__main__":
    import sys
    QCoreApplication.setAttribute(Qt.AA_EnableHighDpiScaling)
    app = QGuiApplication(sys.argv)
    engine = QQmlApplicationEngine()

    model = Model()
    model.addData(Data(44, 33, QColor("red")))
    model.addData(Data(23, 53, QColor("#333")))

    context = engine.rootContext()
    context.setContextProperty('myModel', model)

    engine.load(QUrl.fromLocalFile("main.qml"))

    if len(engine.rootObjects()) == 0:
        sys.exit(-1)

    qsrand(QTime.currentTime().msec())
    timer = QTimer(engine)
    timer.timeout.connect(lambda: model.addData(Data(20 + qrand() % 40, 
                                                     20 + qrand() % 40, 
                                                     QColor(qrand() % 255, qrand() % 255, qrand() % 255))))
    timer.start(1000)

    engine.quit.connect(app.quit)

    sys.exit(app.exec_())

main.qml

import QtQuick.Window 2.2
import QtQuick 2.0
import QtQuick.Controls 1.4

Window {
    visible: true
    id: channels

    Grid {
        columns: 3
        spacing: 9
        Repeater{
        	model: myModel
        	delegate: Rectangle{
        		height: model.height
        		width: model.height
        		color: model.color
        	}
        }
    }
}