# -*- coding: utf-8 -*-

import sys
from PyQt5.QtWidgets import *
from PyQt5.QtCore import *


class FirstWindow(QWidget):

    close_signal = pyqtSignal()
    def __init__(self, parent=None):
        # super這個用法是調用父類的構造函數
        # parent=None表示默認沒有父Widget，如果指定父親Widget，則調用之
        super(FirstWindow, self).__init__
 
(parent)
        self.resize(100, 100)
        self.btn = QToolButton(self)
        self.btn.setText("click")

    def closeEvent(self, event):
        self.close_signal.emit()
        self.close()


class SecondWindow(QWidget):
    def __init__(self, parent=None):
        super(SecondWindow, self).__init__
 
(parent)
        self.resize(200, 200)
        self.setStyleSheet("background: black")

    def handle_click(self):
        if not self.isVisible():
            self.show()

    def handle_close(self):
        self.close()


if __name__ == "__main__":
    App = QApplication(sys.argv)
    ex = FirstWindow()
    s 
 
= SecondWindow()
    ex.btn.clicked.connect(s.handle_click)
    ex.btn.clicked.connect(ex.hide)
    ex.close_signal.connect(ex.close)
    ex.show()
    sys.exit(App.exec_())

pyqt5實現打開子窗口