网络摄像头窗口未打开||请检查代码并告诉我为什么我的相机打不开的错误？

Question

            def face_cropped(img):
                gray=cv2.cvtColor(img,cv2.COLOR_BGR2GRAY)
                faces=face_classifier.detectMultiScale(gray,1.3,5)
                # scaling factor =1.3
                #minimum Neighbour=5

                for(x,y,w,h) in faces:
                    face_cropped=img[y:y+h,x:x+w]
                    return face_cropped

            cap=cv2.VideoCapture(0)
            img_id=0
            while True:
                ret,my_frame=cap.read()
                if face_cropped(my_frame) is not None:
                    img_id+=1
                    face=cv2.resize(face_cropped(my_frame),(450,450))
                    face=cv2.cvtColor(face,cv2.COLOR_BGR2GRAY)
                    file_name_path="data/user."+str(id)+"."+str(img_id)+".jpg"
                    cv2.imwrite(file_name_path,face)
                    cv2.putText(face,str(img_id),(50,50),cv2.FONT_HERSHEY_COMPLEX,2,(0,255,0),2)
                    cv2.imshow("Cropped Face",face)

                if cv2.waitKey(1)==13 or int(img_id)==100:
                    break
            cap.release()
            cv2.destroyAllWindows()
            messagebox.showinfo("Result","Generating dataset is completed !!!!!")

        except Exception as es:
            messagebox.showerror("Error", f"Due to:{str(es)}", parent=self.root)

你能告诉我错误在哪里吗，因为我试图找到很多次但我没有， 这里我的相机窗口没有打开..... 伙计们请帮助我!!!!!!