failed to open a new window after push button pyqt5

Question

i learning pyqt5 and trying to open a new window by click a button from another window. if there are not input() function it will close the open window immediately, so i put input() to keep the window open. the window will open for long, but then it has stopped working. Can some one help me ? Thank you

import sys
from PyQt5.QtWidgets import QApplication, QPushButton,QMainWindow,QWidget
from PyQt5.QtGui import QIcon
from PyQt5.QtCore import pyqtSlot


class App1(QWidget):

    def __init__(self):
        super().__init__()
        self.title = 'open window'
        self.left = 60
        self.top = 60
        self.width = 320
        self.height = 200
        self.initUI()

    def initUI(self):
        self.setWindowTitle(self.title)
        self.setGeometry(self.left, self.top, self.width, self.height)

        self.show()
        m.getch()
        input()                  '''here is the problem'''

class App(QMainWindow):

    def __init__(self):
        super().__init__()
        self.title = 'PyQt5 button - pythonspot.com'
        self.left = 200
        self.top = 200
        self.width = 320
        self.height = 200
        self.initUI()

    def initUI(self):
        self.setWindowTitle(self.title)
        self.setGeometry(self.left, self.top, self.width, self.height)

        button = QPushButton('PyQt5 button', self)
        button.setToolTip('This is an example button')
        button.move(100, 70)
        button.clicked.connect(self.on_click)

        self.show()

    @pyqtSlot()
    def on_click(self):

        app1 = QApplication(sys.argv)
        ex1 = App1()
        sys.exit(app1.exec_())



if __name__ == '__main__':
    app = QApplication(sys.argv)
    ex = App()
    sys.exit(app.exec_())

Answer 1

You need to save a reference to the window or it will be garbage collected when on_click() finishes executing. The easiest way is to store it in App through the use of self

@pyqtSlot()
def on_click(self):
    self.ex1 = App1()

Answer 2

import sys
from PyQt5.QtWidgets import QApplication, QPushButton,QMainWindow,QWidget
from PyQt5.QtGui import QIcon
from PyQt5.QtCore import pyqtSlot

class App1(QWidget):

    def __init__(self):
        super().__init__()
        self.title = 'open window'
        self.left = 60
        self.top = 60
        self.width = 320
        self.height = 200
        self.initUI()

    def initUI(self):
        self.setWindowTitle(self.title)
        self.setGeometry(self.left, self.top, self.width, self.height)

        self.show()
        input()


class App(QMainWindow):

    def __init__(self):
        super().__init__()
        self.title = 'PyQt5 button - pythonspot.com'
        self.left = 200
        self.top = 200
        self.width = 320
        self.height = 200
        self.initUI()

    def initUI(self):
        self.setWindowTitle(self.title)
        self.setGeometry(self.left, self.top, self.width, self.height)

        button = QPushButton('PyQt5 button', self)
        button.setToolTip('This is an example button')
        button.move(100, 70)
        button.clicked.connect(self.on_click)

        self.show()


    @pyqtSlot()
    def on_click(self):
        self.ex1 = App1()

if __name__ == '__main__':
    app = QApplication(sys.argv)
    ex = App()

    sys.exit(app.exec_())