from PyQt5 import QtWidgets, QtGui, QtCore

from myapp import Ui_MainWindow  

import sys

class mywindow(QtWidgets.QMainWindow):

    def __init__(self):

        super(mywindow, self).__init__()

        self.ui = Ui_MainWindow()

        self.ui.setupUi(self)

app = QtWidgets.QApplication([])

application = mywindow()

application.show()

sys.exit(app.exec())