gui界面设计出现了“invalid literal for int() with base 10: ”的问题。

用pycharm做python的gui界面，利用entry.get（）得到键盘输入的答案时，出现了
File "D:\pycharm\djangoProject3\multi_gui.py", line 121, in surecallback
result = int(entry01.get())
ValueError: invalid literal for int() with base 10: ''的报错

困惑：搞不懂自己哪里输入了编译不了的值，系统要报错，不过结果又正常……

import tkinter as tk

import random

import time

window = tk.Tk()

score = 0

count = 1

a = random.randint(1, 9)

b = random.randint(1, 9)

mul01 = tk.StringVar()

mul01.set(str(a))

mul02 = tk.StringVar()

mul02.set(str(b))

count_title = tk.StringVar()

count_title.set('第1道题')

score_lab = tk.StringVar()

score_lab.set('0')

answer_lab = tk.StringVar()


gameover = tk.StringVar()

gameover.set("共测试10道乘法，每题10分，总分100分")

window.title("乘法口诀测试")

window.geometry('600x500')

window["background"] = "LightCyan"

title01 = tk.Label(window,

                   textvariable=gameover,

                   font=('华文行楷', 15),

                   bg='SpringGreen')

title01.place(x=120, y=30)

label01 = tk.Label(window,

                   textvariable=count_title,

                   font=('华文行楷', 20),

                   bg='hotpink')  # 第N道题

label01.place(x=100, y=100)

title02 = tk.Label(window, text="请输入答案：", font=('华文行楷', 20),

                   bg='hotpink')

title02.place(x=80, y=250)

title03 = tk.Label(window,

                   textvariable=score_lab,

                   font=('华文行楷', 28),

                   bg='hotpink')  # 分数lab

title03.place(x=340, y=400)


title04 = tk.Label(window, text="得分：", font=('华文行楷', 28), bg='hotpink')  # 得分lab

title04.place(x=190, y=400)

title05 = tk.Label(window, textvariable=answer_lab, font=('华文行楷', 28), bg='hotpink')  # 得分lab

title05.place(x=220, y=450)

entry01 = tk.Entry(window, textvariable=0, width=10, font=('华文行楷', 20), show=None)  # 文本输入框

entry01.place(x=300, y=250)

label02 = tk.Label(window, textvariable=mul01, font=('华文行楷', 28),

                   bg='hotpink')  # 被乘数lab

label02.place(x=180, y=175)

label03 = tk.Label(window, textvariable=mul02, font=('华文行楷', 28),

                   bg='hotpink')  # 乘数lab

label03.place(x=340, y=175)

imgLabel = tk.Label(window, text='X', font=('黑体', 28),

                    bg='hotpink')  # 乘号标签

imgLabel.place(x=263, y=170)


def surecallback():
    global a, b, count

    for count in range(1, 11):

        product = a * b

        result = int(entry01.get())

        if result == product:

            global score

            score = score + 10

            score_lab.set(str(score))

            answer_lab.set("答对了")

        else:

            answer_lab.set("答错了")

        entry01.delete(0, tk.END)

        a = random.randint(1, 9)

        b = random.randint(1, 9)

        mul01.set(str(a))

        mul02.set(str(b))

        count = count + 1

        c = '第' + str(count) + '道题'

        count_title.set(c)

    gameover.set('测试已结束！')
    count_title.set('第1道题')


button01 = tk.Button(text='确认',

                     font=('华文行楷', 20),

                     width=8,

                     height=1,

                     command=surecallback)

button01.place(x=230, y=310)

window.mainloop()

surecallback函数里为什么要用for循环？
for count in range(1, 11):
这样只有第一次判断的时候有效，判断结束后，entry01.delete(0, tk.END) 就把输入框清空，但是没有退出for循环，所以 result = int(entry01.get()) 里是空字符串，无法转成整数