Как сделать, чтобы динамическое изменение графика функции не продолжалось после очистки графич. поверхности

Как вариант

from PyQt5 import QtCore, QtGui, QtWidgets
from PyQt5.Qt import *
from pyqtgraph import PlotWidget
import numpy as np

class Ui_MainWindow(object):
    def setupUi(self, MainWindow):
        MainWindow.setObjectName("MainWindow")
        MainWindow.resize(1102, 819)
        self.centralwidget = QtWidgets.QWidget(MainWindow)
        self.centralwidget.setStyleSheet("background-color: rgb(10, 170, 0);\n"
"background-color: rgb(73, 152, 255);")
        self.centralwidget.setObjectName("centralwidget")
        self.graphicsView = PlotWidget(self.centralwidget)
        self.graphicsView.setGeometry(QtCore.QRect(420, 30, 621, 631))
        self.graphicsView.setObjectName("graphicsView")
        self.pushButton = QtWidgets.QPushButton(self.centralwidget)
        self.pushButton.setGeometry(QtCore.QRect(30, 500, 341, 41))
        font = QtGui.QFont()
        font.setPointSize(10)
        font.setBold(True)
        font.setWeight(75)
        self.pushButton.setFont(font)
        self.pushButton.setStyleSheet("background: rgb(90, 211, 255)")
        self.pushButton.setObjectName("pushButton")
        self.pushButton_2 = QtWidgets.QPushButton(self.centralwidget)
        self.pushButton_2.setGeometry(QtCore.QRect(30, 610, 341, 41))
        font = QtGui.QFont()
        font.setPointSize(10)
        font.setBold(True)
        font.setWeight(75)
        self.pushButton_2.setFont(font)
        self.pushButton_2.setStyleSheet("background: rgb(90, 211, 255)")
        self.pushButton_2.setObjectName("pushButton_2")
        self.label_4 = QtWidgets.QLabel(self.centralwidget)
        self.label_4.setGeometry(QtCore.QRect(30, 270, 331, 21))
        font = QtGui.QFont()
        font.setPointSize(10)
        font.setBold(True)
        font.setWeight(75)
        self.label_4.setFont(font)
        self.label_4.setObjectName("label_4")
        self.label_5 = QtWidgets.QLabel(self.centralwidget)
        self.label_5.setGeometry(QtCore.QRect(30, 340, 351, 21))
        font = QtGui.QFont()
        font.setPointSize(10)
        font.setBold(True)
        font.setWeight(75)
        self.label_5.setFont(font)
        self.label_5.setObjectName("label_5")
        self.textEdit_6 = QtWidgets.QTextEdit(self.centralwidget)
        self.textEdit_6.setGeometry(QtCore.QRect(30, 450, 221, 31))
        self.textEdit_6.setStyleSheet("background: rgb(255, 255, 255)")
        self.textEdit_6.setObjectName("textEdit_6")
        self.label_6 = QtWidgets.QLabel(self.centralwidget)
        self.label_6.setGeometry(QtCore.QRect(10, 420, 391, 21))
        font = QtGui.QFont()
        font.setPointSize(10)
        font.setBold(True)
        font.setWeight(75)
        self.label_6.setFont(font)
        self.label_6.setObjectName("label_6")
        self.groupBox = QtWidgets.QGroupBox(self.centralwidget)
        self.groupBox.setGeometry(QtCore.QRect(30, 30, 321, 231))
        font = QtGui.QFont()
        font.setPointSize(10)
        self.groupBox.setFont(font)
        self.groupBox.setObjectName("groupBox")
        self.label = QtWidgets.QLabel(self.groupBox)
        self.label.setGeometry(QtCore.QRect(10, 30, 291, 21))
        font = QtGui.QFont()
        font.setPointSize(10)
        font.setBold(True)
        font.setWeight(75)
        self.label.setFont(font)
        self.label.setObjectName("label")
        self.label_2 = QtWidgets.QLabel(self.groupBox)
        self.label_2.setGeometry(QtCore.QRect(10, 100, 291, 21))
        font = QtGui.QFont()
        font.setPointSize(10)
        font.setBold(True)
        font.setWeight(75)
        self.label_2.setFont(font)
        self.label_2.setObjectName("label_2")
        self.label_3 = QtWidgets.QLabel(self.groupBox)
        self.label_3.setGeometry(QtCore.QRect(10, 160, 291, 21))
        font = QtGui.QFont()
        font.setPointSize(10)
        font.setBold(True)
        font.setWeight(75)
        self.label_3.setFont(font)
        self.label_3.setObjectName("label_3")
        self.textEdit_9 = QtWidgets.QTextEdit(self.groupBox)
        self.textEdit_9.setGeometry(QtCore.QRect(10, 190, 221, 31))
        self.textEdit_9.setStyleSheet("background: rgb(255, 255, 255)")
        self.textEdit_9.setObjectName("textEdit_9")
        self.textEdit_10 = QtWidgets.QTextEdit(self.groupBox)
        self.textEdit_10.setGeometry(QtCore.QRect(10, 120, 221, 31))
        self.textEdit_10.setStyleSheet("background: rgb(255, 255, 255)")
        self.textEdit_10.setObjectName("textEdit_10")
        self.textEdit_11 = QtWidgets.QTextEdit(self.groupBox)
        self.textEdit_11.setGeometry(QtCore.QRect(10, 60, 221, 31))
        self.textEdit_11.setStyleSheet("background: rgb(255, 255, 255)")
        self.textEdit_11.setObjectName("textEdit_11")
        self.textEdit_7 = QtWidgets.QTextEdit(self.centralwidget)
        self.textEdit_7.setGeometry(QtCore.QRect(30, 370, 221, 31))
        self.textEdit_7.setStyleSheet("background: rgb(255, 255, 255)")
        self.textEdit_7.setObjectName("textEdit_7")
        self.textEdit_8 = QtWidgets.QTextEdit(self.centralwidget)
        self.textEdit_8.setGeometry(QtCore.QRect(30, 300, 221, 31))
        self.textEdit_8.setStyleSheet("background: rgb(255, 255, 255)")
        self.textEdit_8.setObjectName("textEdit_8")
        self.pushButton_3 = QtWidgets.QPushButton(self.centralwidget)
        self.pushButton_3.setGeometry(QtCore.QRect(30, 560, 341, 41))
        font = QtGui.QFont()
        font.setPointSize(10)
        font.setBold(True)
        font.setWeight(75)
        self.pushButton_3.setFont(font)
        self.pushButton_3.setStyleSheet("background: rgb(90, 211, 255)")
        self.pushButton_3.setObjectName("pushButton_3")
        MainWindow.setCentralWidget(self.centralwidget)
        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", "Аппроксимация функции нейронной сетью"))
        self.pushButton.setText(_translate("MainWindow", "Построить аппроксимацию функции"))
        self.pushButton_2.setText(_translate("MainWindow", "Очистить графич.поверхность"))
        self.label_4.setText(_translate("MainWindow", "Скорость обучения(learning rate)"))
        self.label_5.setText(_translate("MainWindow", "Количество эпох(number of iterations)"))
        self.label_6.setText(_translate("MainWindow", "Количество итераций(number of iterations)"))
        self.groupBox.setTitle(_translate("MainWindow", "Количество нейронов в каждом слое"))
        self.label.setText(_translate("MainWindow", "Входной слой(Input Layer)"))
        self.label_2.setText(_translate("MainWindow", "Скрытый слой(Hidden Layer)"))
        self.label_3.setText(_translate("MainWindow", "Выходной слой(Output Layer)"))
        self.pushButton_3.setText(_translate("MainWindow", "Остановить процесс аппроксимации"))

#Модифицированная нейросеть
class PartyNN(object):
    
    def __init__(self, learning_rate=0.1, input_nodes=1, hidden_nodes=5, output_nodes=1):
        input_nodes+=1
        self.weights_0_1 = np.random.normal(0.0, hidden_nodes ** -0.5, (hidden_nodes, input_nodes))
        self.weights_1_2 = np.random.normal(0.0, output_nodes ** -0.5, (output_nodes, hidden_nodes))
        self.sigmoid_mapper = np.vectorize(self.sigmoid)
        self.learning_rate = np.array([learning_rate])
        
    def set_lr(lr):
        self.learning_rate = np.array([lr])
        
    def sigmoid(self, x):
        return 1 / (1 + np.exp(-x))
    
    def predict(self, inputs):
        inputs = np.concatenate((inputs,[1]))
        inputs_1 = np.dot(self.weights_0_1, inputs)
        outputs_1 = self.sigmoid_mapper(inputs_1)
        
        inputs_2 = np.dot(self.weights_1_2, outputs_1)
        #outputs_2 = self.sigmoid_mapper(inputs_2)
        outputs_2 = inputs_2
        return outputs_2
    
    def train(self, inputs, expected_predict):
        inputs = np.concatenate((inputs,[1]))        
        inputs_1 = np.dot(self.weights_0_1, inputs)
        outputs_1 = self.sigmoid_mapper(inputs_1)
        
        inputs_2 = np.dot(self.weights_1_2, outputs_1)
        #outputs_2 = self.sigmoid_mapper(inputs_2)
        outputs_2 = inputs_2
        actual_predict = outputs_2[0]
        
        error_layer_2 = np.array([actual_predict - expected_predict])
        gradient_layer_2 = 1 # Здесь что-то я не так сделал. Нужно учитывать вес# actual_predict * (1 - actual_predict)
        weights_delta_layer_2 = error_layer_2 * gradient_layer_2  
        self.weights_1_2 -= (np.dot(weights_delta_layer_2, outputs_1.reshape(1, len(outputs_1)))) * self.learning_rate
        
        error_layer_1 = weights_delta_layer_2 * self.weights_1_2
        gradient_layer_1 = outputs_1 * (1 - outputs_1)
        weights_delta_layer_1 = error_layer_1 * gradient_layer_1
        self.weights_0_1 -= np.dot(inputs.reshape(len(inputs), 1), weights_delta_layer_1).T  * self.learning_rate

class MainWindow(QtWidgets.QMainWindow, Ui_MainWindow):
    def __init__(self):
        super().__init__()
        self.setupUi(self)

#        self.pushButton.clicked.connect(self.draw)                       # ---
        self.pushButton.clicked.connect(self.start_func)                  # +++
        self.pushButton_2.clicked.connect(self.clear)                     # !!!
        self.pushButton_3.clicked.connect(self.stop_start)  

# ----> vvvvvvvvvvvvvv <------------------------------------------------- # +++
    def initMainWindow(self):                                        
        self.flag = True                                       
        self.pcenter = 0
        self.prange = 10
        self.step = 0.1
        period  = np.arange(self.pcenter-self.prange, self.pcenter+self.prange, self.step)
        lr = 0.00005
        self.myNN = PartyNN(learning_rate=lr, input_nodes=1, hidden_nodes=50, output_nodes=1)
        self.set_count = 100
        rand_set = np.random.random(self.set_count)*2*self.prange-self.prange+self.pcenter

    def start_func(self):                                                  # +++
        self.initMainWindow()                                              # +++
        self.draw()                                                        # +++
    
    def clear(self):
        self.flag = False                                                  # +++
#        self.graphicsView.clear()                                         # ---
        QtCore.QTimer.singleShot(4000, self.graphicsView.clear)            # +++
        
    def stop_start(self): 
        self.flag = not self.flag
        if self.flag:
           self.pushButton_3.setText("Остановить процесс аппроксимации")
           self.draw() 
        else:
            self.pushButton_3.setText("Возобновить процесс аппроксимации") 
    
    #Тестовая функция
    def ApproxFunc(self,x):
        return np.sin(x)*10 + x**2
    
    #Функция обучения
    def Train(self):
        rand_set = np.random.random(self.set_count)*2*self.prange-self.prange+self.pcenter
        for x in range(0, self.set_count-1):
            self.myNN.train([rand_set[x]], self.ApproxFunc(rand_set[x]))

    def MSE(y, Y):
        return np.mean((y-Y)**2)

    def draw(self):
        period  = np.arange(self.pcenter-self.prange, self.pcenter+self.prange, self.step)
        epochs = 100
        for e in range(epochs):
           for tr in range(100):
               self.Train() 
               app.processEvents()                                                
               if not self.flag:                                          
                   break                                                  
#          self.clear()                                                        # ---
           self.graphicsView.clear()                                           # +++
           
           self.graphicsView.plot(period, self.ApproxFunc(period),pen=(1,3))
           
           rand_set = np.random.random(self.set_count)*2*self.prange-self.prange+self.pcenter
           result_set=np.zeros(100)
           MSE = 0
           for x in range(0, 50):
               result_set[x] = self.myNN.predict([rand_set[x]])
               MSE += (self.ApproxFunc(rand_set[x]) - result_set[x])**2
               self.graphicsView.plot([rand_set[x]],[result_set[x]], pen=(1,2),symbol='o')               
               app.processEvents()                                         
           if not self.flag:                                              
               break                                                       
    
    def closeEvent(self, event):
        reply = QMessageBox.question\
        (self, 'Информация',
            "Вы уверены, что хотите уйти?",
             QMessageBox.Yes,
             QMessageBox.No)
        if reply == QMessageBox.Yes:
            self.flag = False
            event.accept()
        else:
            event.ignore()


if __name__ == "__main__":
    import sys
    app = QtWidgets.QApplication(sys.argv)
    w = MainWindow()
    w.show()
    sys.exit(app.exec_())