PySide2 QML boiler plate

main.py

# This Python file uses the following encoding: utf-8

# https://qmlbook.github.io/ch18-python/python.html
# This bug has already been fixed
# We can connect in QML
# https://bugreports.qt.io/browse/PYSIDE-634

# https://wiki.qt.io/Qt_for_Python_Signals_and_Slots

import sys
import random
# from PySide2.QtWidgets import QApplication
# QGuiApplication - base class + GUI capabilities. Use it in QML applications.
# QApplication - base class + GUI + support for widgets.
# Use it in QtWidgets applications.
from PySide2.QtGui import QGuiApplication
from PySide2.QtQml import QQmlApplicationEngine
from PySide2.QtCore import QUrl, QObject, Signal, Slot


class NumberGenerator(QObject):

    nextNumber = Signal(int, name="nextNumber", arguments=['number'])

    def __init__(self):
        QObject.__init__(self)

    @Slot()
    def giveNumber(self):
        self.nextNumber.emit(random.randint(0, 99))


if __name__ == '__main__':
    app = QGuiApplication(sys.argv)
    # app = QApplication([])
    engine = QQmlApplicationEngine()

    number_generator = NumberGenerator()
    engine.rootContext().setContextProperty("numberGenerator", number_generator)

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

    if not engine.rootObjects():
        sys.exit(-1)

    sys.exit(app.exec_())

main.pyproject

{
    "files": ["main.py","main.qml"]
}

main.qml

import QtQuick 2.0
import QtQuick.Window 2.0
import QtQuick.Controls 2.0

Window {
    id: root

    width: 640
    height: 480
    visible: true
    title: "Hello Python World!"

    Flow {
        Button {
            text: "Give me a number!"
            onClicked: numberGenerator.giveNumber();
        }
        Label {
            id: numberLabel
            text: "no number"
        }

        Connections {
            target: numberGenerator
            onNextNumber: {
                numberLabel.text = number
            }
        }
    }
}