self.close and self.hide not working in pyqt5

Question

I am new to python. I am using pyqt5 for GUI development. I have a main Window which should close and new dialog appears after clicking the pushButton. But it doesnot closes and neither show any error and opens the nextDialog. I also want to close nextDialog when OK button is clicked in nextDialog. Please help to check the issue. I am trying to develeop a new project but stuck on this issue. Codes are given below.

Main.py

from PyQt5 import QtCore, QtGui, QtWidgets
from nextDialog import Ui_Dialog

class Ui_MainWindow(QtWidgets.QMainWindow):
    def setupUi(self, MainWindow):
        MainWindow.setObjectName("MainWindow")
        MainWindow.resize(370, 171)
        self.centralwidget = QtWidgets.QWidget(MainWindow)
        self.centralwidget.setObjectName("centralwidget")
        self.pushButton = QtWidgets.QPushButton(self.centralwidget)
        self.pushButton.setGeometry(QtCore.QRect(110, 50, 75, 23))
        self.pushButton.setObjectName("pushButton")
        MainWindow.setCentralWidget(self.centralwidget)

        self.pushButton.clicked.connect(self.opennext)

        self.retranslateUi(MainWindow)
        QtCore.QMetaObject.connectSlotsByName(MainWindow)

    def opennext(self):
        self.Dialog = QtWidgets.QDialog()
        self.ui = Ui_Dialog()
        self.ui.setupUi(self.Dialog)
        self.Dialog.show()
        self.close() #Not working

    def retranslateUi(self, MainWindow):
        _translate = QtCore.QCoreApplication.translate
        MainWindow.setWindowTitle(_translate("MainWindow", "MainWindow"))
        self.pushButton.setText(_translate("MainWindow", "Open"))


if __name__ == "__main__":
    import sys
    app = QtWidgets.QApplication(sys.argv)
    MainWindow = QtWidgets.QMainWindow()
    ui = Ui_MainWindow()
    ui.setupUi(MainWindow)
    MainWindow.show()
    sys.exit(app.exec_())

    from PyQt5 import QtCore, QtGui, QtWidgets
    import sys

nextDialog.py

class Ui_Dialog(QtWidgets.QMainWindow):
    def setupUi(self, Dialog):
    Dialog.setObjectName("Dialog")
    Dialog.resize(346, 182)
    self.pushButton = QtWidgets.QPushButton(Dialog)
    self.pushButton.setGeometry(QtCore.QRect(110, 80, 75, 23))
    self.pushButton.setObjectName("pushButton")

    self.pushButton.clicked.connect(self.exit)

    self.retranslateUi(Dialog)
    QtCore.QMetaObject.connectSlotsByName(Dialog)

    def exit(self):
        self.hide() #This also not working, I want either of these two to 
                    #work

    def retranslateUi(self, Dialog):
        _translate = QtCore.QCoreApplication.translate
        Dialog.setWindowTitle(_translate("Dialog", "Dialog"))
        self.pushButton.setText(_translate("Dialog", "OK"))

Answer 1

Try it:

main.py

from PyQt5 import QtCore, QtGui, QtWidgets
from nextDialog import Ui_Dialog

class MainWindow(QtWidgets.QMainWindow):
    def __init__(self):
        super().__init__()
        self.centralwidget = QtWidgets.QWidget()
        self.setCentralWidget(self.centralwidget)
        self.pushButton = QtWidgets.QPushButton("Open", self.centralwidget)
        self.pushButton.setGeometry(QtCore.QRect(110, 50, 75, 23))

        self.pushButton.clicked.connect(self.opennext)

    def opennext(self):
        self.Dialog = QtWidgets.QDialog()
        self.ui = Ui_Dialog()
        self.ui.setupUi(self.Dialog)
        self.Dialog.show()
        self.close() #Not working

if __name__ == "__main__":
    import sys
    app = QtWidgets.QApplication(sys.argv)
    window = MainWindow()
#    ui = Ui_MainWindow()
#    ui.setupUi(MainWindow)
    window.show()
    sys.exit(app.exec_())

nextDialog.py

import sys
from PyQt5 import QtCore, QtGui, QtWidgets

class Ui_Dialog(QtWidgets.QMainWindow):
    def setupUi(self, Dialog):
        Dialog.setObjectName("Dialog")
        Dialog.resize(346, 182)
        self.pushButton = QtWidgets.QPushButton(Dialog)
        self.pushButton.setGeometry(QtCore.QRect(110, 80, 75, 23))
        self.pushButton.setObjectName("pushButton")

        self.pushButton.clicked.connect(Dialog.close)      # <---

        self.retranslateUi(Dialog)
        QtCore.QMetaObject.connectSlotsByName(Dialog)

    def retranslateUi(self, Dialog):
        _translate = QtCore.QCoreApplication.translate
        Dialog.setWindowTitle(_translate("Dialog", "Dialog"))
        self.pushButton.setText(_translate("Dialog", "OK"))

Answer 2

Hi kind of difficult to understand your code, I am using just Designer to make my GUI,

in anycase I made the first part of the puzzle work for your main.py

line 4 should read class Ui_MainWindow(object):

and to close the first window about lane 25 use MainWindow.close()

added import sys too at the beginning, here the code

main.py:

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""
Created on Sat Apr 18 17:43:19 2020

@author: Pietro
"""

import sys
from PyQt5 import QtCore, QtGui, QtWidgets
from nextDialog import Ui_Dialog

class Ui_MainWindow(object):
    def setupUi(self, MainWindow):
        MainWindow.setObjectName("MainWindow")
        MainWindow.resize(370, 171)
        self.centralwidget = QtWidgets.QWidget(MainWindow)
        self.centralwidget.setObjectName("centralwidget")
        self.pushButton = QtWidgets.QPushButton(self.centralwidget)
        self.pushButton.setGeometry(QtCore.QRect(110, 50, 75, 23))
        self.pushButton.setObjectName("pushButton")
        MainWindow.setCentralWidget(self.centralwidget)

        self.pushButton.clicked.connect(self.opennext)

        self.retranslateUi(MainWindow)
        QtCore.QMetaObject.connectSlotsByName(MainWindow)

    def opennext(self):
        self.Dialog = QtWidgets.QDialog()
        self.ui = Ui_Dialog()
        self.ui.setupUi(self.Dialog)
        self.Dialog.show()
        MainWindow.close()

    def retranslateUi(self, MainWindow):
        _translate = QtCore.QCoreApplication.translate
        MainWindow.setWindowTitle(_translate("MainWindow", "MainWindow"))
        self.pushButton.setText(_translate("MainWindow", "Open"))


if __name__ == "__main__":
    app = QtWidgets.QApplication(sys.argv)
    MainWindow = QtWidgets.QMainWindow()
    ui = Ui_MainWindow()
    ui.setupUi(MainWindow)
    MainWindow.show()
    sys.exit(app.exec_())

this open first window then close it when open buttton is pressed and new window appears, second part of the riddle is gonna take longer I'll try it as soon as I get some spare time

Dialog.py from answer below seems to work dont know why (dont know how main.py works too, but it is kind of more illogic to me the fact that def exit doesnt work).

nextDialog.py

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""
Created on Sat Apr 18 17:43:19 2020

@author: Pietro
"""

import sys
from PyQt5 import QtCore, QtGui, QtWidgets



class Ui_Dialog(QtWidgets.QMainWindow):
    def setupUi(self, Dialog):
        Dialog.setObjectName("Dialog")
        Dialog.resize(346, 182)
        self.pushButton = QtWidgets.QPushButton(Dialog)
        self.pushButton.setGeometry(QtCore.QRect(110, 80, 75, 23))
        self.pushButton.setObjectName("pushButton")

        self.pushButton.clicked.connect(Dialog.close)  # as answer below dont know why def  exit doesnt work

        self.retranslateUi(Dialog)
        QtCore.QMetaObject.connectSlotsByName(Dialog)


#    def exit(self):
#        print('exit' *5)
#        Dialog.close()

    def retranslateUi(self, Dialog):
        _translate = QtCore.QCoreApplication.translate
        Dialog.setWindowTitle(_translate("Dialog", "Dialog"))
        self.pushButton.setText(_translate("Dialog", "OK"))