In Python, how to use GUI module file created in QtDesigner - python-3.x

Question

I created a GUI with the hepl of QtCreator-->QtDesigner. The file is called mainwindow.ui. With the help of pyuic5 I created mainwindow.py
pyuic5 mainwindow.ui > mainwindow.py
and this is how it looks like:
from PyQt5 import QtCore, QtGui, QtWidgets
class Ui_MainWindow(object):
def setupUi(self, MainWindow):
MainWindow.setObjectName("MainWindow")
MainWindow.resize(400, 300)
self.centralWidget = QtWidgets.QWidget(MainWindow)
self.centralWidget.setObjectName("centralWidget")
self.frame = QtWidgets.QFrame(self.centralWidget)
self.frame.setGeometry(QtCore.QRect(30, 20, 341, 191))
self.frame.setFrameShape(QtWidgets.QFrame.Panel)
self.frame.setFrameShadow(QtWidgets.QFrame.Sunken)
self.frame.setObjectName("frame")
MainWindow.setCentralWidget(self.centralWidget)
self.menuBar = QtWidgets.QMenuBar(MainWindow)
self.menuBar.setGeometry(QtCore.QRect(0, 0, 400, 23))
self.menuBar.setObjectName("menuBar")
MainWindow.setMenuBar(self.menuBar)
self.mainToolBar = QtWidgets.QToolBar(MainWindow)
self.mainToolBar.setObjectName("mainToolBar")
MainWindow.addToolBar(QtCore.Qt.TopToolBarArea, self.mainToolBar)
self.statusBar = QtWidgets.QStatusBar(MainWindow)
self.statusBar.setObjectName("statusBar")
MainWindow.setStatusBar(self.statusBar)
self.retranslateUi(MainWindow)
QtCore.QMetaObject.connectSlotsByName(MainWindow)
def retranslateUi(self, MainWindow):
_translate = QtCore.QCoreApplication.translate
MainWindow.setWindowTitle(_translate("MainWindow", "MainWindow"))
and wanted to import that in my main script main.py:
#!/usr/bin/env python3
from PyQt5.QtCore import *
from PyQt5.QtGui import *
from PyQt5.QtWidgets import *
from mainwindow import *
import sys
def main():
app = QApplication(sys.argv)
instance = Ui_MainWindow()
#instance.show()
sys.exit(app.exec_())
if __name__ == "__main__":
main()
...but nothing happens when I run it. How should my main.py look like to use that gui module?

Answer 1

Ok, I figured it myself. To use a GUI file in Python, created in QtCreator called mainwindow.py, my main.py should look something like this:
#!/usr/bin/env python3
from PyQt5.QtCore import *
from PyQt5.QtGui import *
from PyQt5.QtWidgets import *
from mainwindow import *
import sys
class Main(QMainWindow):
def __init__(self):
super().__init__()
self.ui = Ui_MainWindow()
self.ui.setupUi(self)
self.show()
def main():
app = QApplication(sys.argv)
instance = Main()
#instance.show()
sys.exit(app.exec_())
if __name__ == "__main__":
main()
My class Main(QMainWindow) must have a parent QMainWindow and not QWidget because QWidget doesn't have setCentralWidget method which is needed in mainwindow.py.