application.py

from PyQt5.QtCore import *
from PyQt5.QtGui import *
from PyQt5.QtMultimedia import *
from PyQt5.QtQml import QQmlApplicationEngine


def ListModelFor(klass):
    class ListModel(QAbstractItemModel):

        def __init__(self):
            super().__init__()
            self._items = []

            meta = klass().metaObject()

            self._roleNames = {}
            for i in range(0, meta.propertyCount()):
                self._roleNames[i] = meta.property(i).name().encode('utf-8')

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

        def columnCount(self, parent=QModelIndex()):
            return 1

        def parent(self, index):
            return QModelIndex()

        def roleNames(self):
            return self._roleNames

        def data(self, index, role):
            item = self._items[index.row()]
            return item.property(self._roleNames[role])

        def index(self, row, column=0, parent=QModelIndex()):
            return self.createIndex(row, column, parent)

        def append(self, item):
            index = self.rowCount()
            self.beginInsertRows(QModelIndex(), index, index)
            self._items.append(item)
            self.endInsertRows()

        def update(self, index, item):
            self._items[index] = item
            self.dataChanged.emit(self.index(index), self.index(index))

        def remove(self, item):
            index = self._items.index(item)
            self.beginRemoveRows(QModelIndex(), index, index)
            self._items.remove(item)
            self.endRemoveRows()

    return ListModel


class ComboItem(QObject):

    def __init__(self, name=None, value=None, extra=None, parent=None):
        super().__init__(parent)
        self._name = name
        self._value = value
        self._extra = extra

    @pyqtProperty(str)
    def name(self):
        return self._name

    @name.setter
    def name(self, value):
        self._name = value

    @pyqtProperty(str)
    def value(self):
        return self._value

    @value.setter
    def value(self, value):
        self._value = value

    @pyqtProperty(str)
    def extra(self):
        return self._extra

    @extra.setter
    def extra(self, value):
        self._extra = value


class ComboItemListModel(ListModelFor(ComboItem)):

    clicked = pyqtSignal()

    def __init__(self):
        super().__init__()
        self.clicked.connect(self._on_clicked)

    def _on_clicked(self):
        for i in self._items:
            print(i.__dict__)


class Application(QGuiApplication):

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.mainWindow = MainWindow(self)

    def start(self):
        self.mainWindow.show()


class MainWindow(QObject):

    clicked = pyqtSignal()

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

        self.clicked.connect(self._on_clicked)

        self.items = ComboItemListModel()

        self.items.append(ComboItem('first', '1', 'extra one'))
        self.items.append(ComboItem('second', '2', 'extra two'))
        self.items.append(ComboItem('third', '3', 'extra three'))

        self.engine = QQmlApplicationEngine(self)

        ctx = self.engine.rootContext()
        ctx.setContextProperty('items', self.items)
        ctx.setContextProperty('main', self)

        self.engine.quit.connect(parent.quit)
        self.engine.load(QUrl.fromLocalFile('Application.qml'))

        self.window = self.engine.rootObjects()[0]

    def _on_clicked(self):
        n = self.items.rowCount()+1
        self.items.append(ComboItem('%s th'%n, str(n), 'extra one'))

    def show(self):
        self.window.show()

Application.qml

import QtQuick 2.2
import QtQuick.Window 2.1
import QtQuick.Controls 1.1
import QtQuick.Controls.Styles 1.2
import QtMultimedia 5.0
import QtQuick.Layouts 1.11

Window {
    id: mainWindow
    title: "QApplication"

    width: 800
    height: 600

    flags: Qt.Window
    color: "#333"

    Action {
        id: closeWindow
        shortcut: "Esc"
        onTriggered: Qt.quit();
    }

    ComboBox {
        model: items
        implicitWidth: 200
        anchors.centerIn: parent
        textRole: "name"
    }

    RowLayout {
        Button {
            text: "Main"
            onClicked: {
                main.clicked()
            }
        }
        Button {
            text: "Items"
            onClicked: {
                items.clicked()
            }
        }
    }
}

main.py

#!env python3

import sys
import asyncio

from quamash import QEventLoop
from application import Application

try:
    # handle ctrl+c on Linux
    import signal
    signal.signal(signal.SIGINT, signal.SIG_DFL)
except ImportError:
    pass


if __name__ == '__main__':
    app = Application(sys.argv)

    loop = QEventLoop(app)
    asyncio.set_event_loop(loop)

    app.start()
    sys.exit(loop.run_forever())