import sys
                from PyQt5.QtWidgets import QWidget, QPushButton,QHBoxLayout, QGridLayout, QApplication

                class UI(QWidget):

                    def __init__(self):
                        super().__init__()
                        self.initUI()

                    def initUI(self):
                        self.addButton = QPushButton("add")
                        #once click the addButton, call add() function
                        self.addButton.clicked.connect(self.add)

                        self.delButton = QPushButton("delete")
                        self.delButton.clicked.connect(self.delete)

                        self.layout = QGridLayout()
                        self.layout.addWidget(self.addButton, 0, 0)
                        self.layout.addWidget(self.delButton, 0, 1)

                        self.setLayout(self.layout)

                        self.setWindowTitle('add')
                        self.show()

                    def add(self):
                        Button1 = QPushButton("1")
                        self.layout.addWidget(Button1, 1, 0)

                        Button2 = QPushButton("2")
                        self.layout.addWidget(Button2, 1, 1)

                    def delete(self):
                        #the indexes of widgets we want to remove is 2 and 3
                        self.layout.itemAt(2).widget().deleteLater()
                        self.layout.itemAt(3).widget().deleteLater()


                if __name__ == '__main__':
                    app = QApplication(sys.argv)
                    ex = UI()
                    sys.exit(app.exec_())