怎么通过点击button，来打开一个新的窗口？

是写在同一个脚本里，还是把新窗口的代码放在另一个脚本里，然后通过点击按钮来运行？

import sys

from PyQt5.QtWidgets import *

from PyQt5.QtGui import *

class FirstWindow(QWidget):

def __init__(self):

super().__init__()

self.windowUI()

def windowUI(self):

self.setWindowTitle("Login")

self.textfield()

self.center()

def center(self):

qr = self.frameGeometry()

cp = QDesktopWidget().availableGeometry().center()

qr.moveCenter(cp)

self.move(qr.topLeft())

def textfield(self):

QToolTip.setFont(QFont('SansSerif', 12))

user = QLabel("User:")

userEdit = QLineEdit()

userEdit.setToolTip("请输入你的帐号")

passWord = QLabel("PassWord:")

passWordEdit = QLineEdit()

passWordEdit.setToolTip("请输入你的密码")

grid = QGridLayout()

grid.setSpacing(0)

grid.addWidget(user, 0, 0)

grid.addWidget(userEdit, 1, 0)

grid.addWidget(passWord, 2, 0)

grid.addWidget(passWordEdit, 3, 0)

empty = QLabel()

grid.addWidget(empty, 4, 0)

btn_logon = QPushButton("Log on")

btn_quit = QPushButton("Quit")

grid.addWidget(btn_logon, 5, 0, 1, 2)

grid.addWidget(btn_quit, 6, 0, 1, 2)

btn_logon.clicked.connect(self.onclick)

btn_quit.clicked.connect(quit)

self.setLayout(grid)

def onclick(self):

newWindow = SecondWindow()

newWindow.show()

newWindow.exec_()

class SecondWindow(QWidget):

def __init__(self):

super().__init__

self.newWindowUI

def newWindowUI(self):

self.resize(300,300)

self.move(200,200)

if __name__ == "__main__":

App = QApplication(sys.argv)

ex = FirstWindow()

ex.show()

sys.exit(App.exec_())