How to open a window on a button click in PyQt5?

Question

Python

I have a window that needs to be opened on click of an ok button in pyqt5. There's no way I can do it.
Here is the window code:

from PySide import QtCore, QtGui

class Ui_FirstWindow(object):
    def setupUi(self, Dialog):
        Dialog.setObjectName("Dialog")
        Dialog.resize(191, 100)
        font = QtGui.QFont()
        font.setFamily("Arial")
        font.setPointSize(9)
        font.setWeight(75)
        font.setBold(True)
        Dialog.setFont(font)
        Dialog.setStyleSheet("QDialog{\n"
"background: \"#363a45\";\n"
"}\n"
"QGroupBox{\n"
"color: \"#b4bbd4\";\n"
"font-weight: bold;\n"
"border-width: 1px;\n"
"border-radius: 1px;\n"
"border-color: black;\n"
"border-style: solid;\n"
"}\n"
"")
        self.groupBox = QtGui.QGroupBox(Dialog)
        self.groupBox.setGeometry(QtCore.QRect(-1, 9, 191, 31))
        self.groupBox.setTitle("")
        self.groupBox.setObjectName("groupBox")
        self.label = QtGui.QLabel(self.groupBox)
        self.label.setGeometry(QtCore.QRect(60, 5, 131, 21))
        font = QtGui.QFont()
        font.setFamily("Arial Black")
        font.setPointSize(10)
        font.setWeight(75)
        font.setBold(True)
        self.label.setFont(font)
        self.label.setStyleSheet("color:white")
        self.label.setObjectName("label")
        self.label_2 = QtGui.QLabel(Dialog)
        self.label_2.setGeometry(QtCore.QRect(30, 39, 131, 31))
        font = QtGui.QFont()
        font.setFamily("Arial")
        font.setPointSize(10)
        font.setWeight(75)
        font.setBold(True)
        self.label_2.setFont(font)
        self.label_2.setStyleSheet("color:white")
        self.label_2.setObjectName("label_2")
        self.label_3 = QtGui.QLabel(Dialog)
        self.label_3.setGeometry(QtCore.QRect(50, 70, 121, 20))
        font = QtGui.QFont()
        font.setFamily("Arial")
        font.setPointSize(10)
        font.setWeight(75)
        font.setBold(True)
        self.label_3.setFont(font)
        self.label_3.setStyleSheet("color:white")
        self.label_3.setObjectName("label_3")

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

    def retranslateUi(self, Dialog):
        Dialog.setWindowTitle(QtGui.QApplication.translate("Dialog", "Dialog", None, QtGui.QApplication.UnicodeUTF8))
        self.label.setText(QtGui.QApplication.translate("Dialog", "Ошибка!", None, QtGui.QApplication.UnicodeUTF8))
        self.label_2.setText(QtGui.QApplication.translate("Dialog", "Формат телефона:", None, QtGui.QApplication.UnicodeUTF8))
        self.label_3.setText(QtGui.QApplication.translate("Dialog", "7xxxxxxxxxx", None, QtGui.QApplication.UnicodeUTF8))


if __name__ == "__main__":
    import sys
    app = QtGui.QApplication(sys.argv)
    Dialog = QtGui.QDialog()
    ui = Ui_Dialog()
    ui.setupUi(Dialog)
    Dialog.show()
    sys.exit(app.exec_())

Answer 1

Opa ... what is it?