需要帮助理解python中的错误文本：

Question

Ok so basically I wrote a not very pretty GUI that gives random simple math questions. It works just like I want it to. However the idle Shell spits out red at me every time I click enter. Despite that, like I said, it continues to function as I want it to. So I'm having trouble understanding why this specific part of my code is causing problems. Apologies for the long section of code:

from tkinter import Label, Frame, Entry, Button, LEFT, RIGHT, END
from tkinter.messagebox import showinfo
import random

class Ed(Frame):
    'Simple arithmetic education app'
    def __init__(self,parent=None):
        'constructor'
        Frame.__init__(self, parent)
        self.pack()
        self.tries = 0
        Ed.make_widgets(self)
        Ed.new_problem(self)

    def make_widgets(self):
        'defines Ed widgets'
        self.entry1 = Entry(self, width=20, bg="gray", fg ="black")
        self.entry1.grid(row=0, column=0, columnspan=4)
        self.entry1.pack(side = LEFT)
        self.entry2 = Entry(self, width=20, bg="gray", fg ="black")
        self.entry2.grid(row=2, column=2, columnspan=4)
        self.entry2.pack(side = LEFT)
        Button(self,text="ENTER", command=self.evaluate).pack(side = RIGHT)

    def new_problem(self):
        'creates new arithmetic problem'
        opList = ["+", "-"]
        a = random.randrange(10+1)
        b = random.randrange(10+1)
        op = random.choice(opList)
        if b > a:
            op = "+"
        self.entry1.insert(END, a)
        self.entry1.insert(END, op)
        self.entry1.insert(END, b)


    def evaluate(self):
        'handles button "Enter" clicks by comparing answer in entry to correct result'
        result = eval(self.entry1.get())
        if result == eval(self.entry2.get()):
            self.tries += 1
            showinfo(title="Huzzah!", message="That's correct! Way to go! You got it in {} tries.".format(self.tries))
            self.entry1.delete(0, END)
            self.entry2.delete(0, END)
            self.entry1.insert(END, self.new_problem())
        else:
            self.tries += 1
            self.entry2.delete(0, END)

This is the message I get:

Exception in Tkinter callback
Traceback (most recent call last):
  File "C:\Python32\lib\tkinter\__init__.py", line 1399, in __call__
    return self.func(*args)
  File "C:\Python32\Python shit\csc242hw4\csc242hw4.py", line 55, in evaluate
    self.entry1.insert(END, self.new_problem())
  File "C:\Python32\lib\tkinter\__init__.py", line 2385, in insert
    self.tk.call(self._w, 'insert', index, string)
_tkinter.TclError: wrong # args: should be ".52882960.52883240 insert index text"

Answer 1

The error message says that Tkinter thinks it's getting the wrong number of args.

Looking further back in the traceback we see this line caused the error:

File "C:\Python32\Python shit\csc242hw4\csc242hw4.py", line 55, in evaluate
    self.entry1.insert(END, self.new_problem())

But that seems like the right number of arguments! So what's going on?

The problem is that self.new_problem() returns None . It looks like Python's wrapper around Tkinter doesn't pass on the argument when it is None .

To fix this get rid of the call to insert and change line 55 to

self.new_problem()

This works because you are already calling self.entry.insert from inside new_problem .