在Python中使用Tkinter创建一个简单的数学GUI程序

Question

我是python的新手，无法理解此代码出了什么问题 这是错误：

Exception in Tkinter callback
Traceback (most recent call last):

File "C:\Users\sarvinoz.toshpulotov\AppData\Local\Programs\Python\Python37-32\lib\tkinter\__init__.py", line 1705, in __call__

    return self.func(*args)

File "C:/Users/sarvinoz.toshpulotov/Desktop/PROJECT2/Project.py", line 34, in getter

     a[int(coef1.get())] = int(pow1.get())
ValueError: invalid literal for int() with base 10: ''

这是我的代码的一部分：

from tkinter import *

class Derivat:

    def length():
        l = w
        global numb
        frame1 = Frame(l)
        title = Label(frame1, text = "Enter the length of your expression:", font= ("arial", 14), bg = "skyblue")
        title.grid(row = 0, column = 0, padx = 5, pady = 5)
        numb = Entry(frame1, width = 10)
        numb.grid(row=0, column=2)
        frame1.pack(side=TOP, pady=5, padx=5, ipadx = 5, ipady = 5)
        result = Button(frame1, text="Enter:", bg="green")
        result.grid(row=0, column=3, padx =10, pady =10)
        result.config(command=Derivat.getter)

    def getter():
        m = w
        f = int(numb.get())
        frame2 = Frame(m)
        frame3 = Frame(m)
        a = {}
        coef = Label(frame2, text="Enter your coefficients accordingly:")
        coef.grid(row=0, column=0)
        power = Label(frame3, text="Enter the power's of the x accordingly:")
        power.grid(row=10, column=0)
        for i in range(f):
            coef1 = Entry(frame2)
            coef1.grid(row=20, column=i)
            pow1 = Entry(frame3)
            pow1.grid (row = 30, column = i)
            a[int(coef1.get())] = int(pow1.get())
        frame2.pack(side=LEFT, pady=5, padx=5, ipadx=5, ipady=5)
        frame3.pack(side=LEFT, pady=5, padx=5, ipadx=5, ipady=5)
        print(a)