单击 Tkinter 中的按钮时程序无响应？

Question

I'm trying to create a simple calculator using Tkinter, but I'm facing a problem. First see the relevant code:

entry_text = StringVar()
inout = Entry(root, textvariable=entry_text)
inout.grid(row=0, column=0, columnspan=4, sticky="nsew")

def equals():
    print("Equal button is clicked")
    get_answer = True

def divide():
    tempvar = entry_text.get()
    num1 = int(tempvar)
    entry_text.set("")
    while get_answer == False:
        tempvar2 = entry_text.get()
        try:
            num2 = int(tempvar2)
        except ValueError:
            num2 = 0
    print("I'm out of the loop.")
    answer = num1 / num2
    entry_text.set(answer)

Here I'm creating a function for the divide button. The functionality of the button is whenever you click on the button, it takes the instantaneous value of the entry_text variable, stores it in a temporary variable and resets the value of entry_text variable. Then it runs a loop for collecting the next value of entry_text until the equal button is clicked. But the problem lies just here. Whenever I click on divide button, the GUI becomes unresponsive, and I don't get to enter the next value for the divide operation and get out of the loop.

Can anyone help?

Answer 1

Avoid using while loop in a tkinter application because it will block tkinter mainloop from handling pending events.

Also, get_answer inside equals() is a local variable because you haven't declare it as a global using global get_answer .

Actually you should perform the required operation inside equals() , but you need to store the first number and selected operation as global variables:

num1 = 0
operator = None

def equals():
    global num1, operator
    print("Equal button is clicked")
    try:
        tempvar = entry_text.get()
        num2 = float(tempvar)  # used float() instead of int()
        if operator == '/' and num2 != 0:
            answer = num1 / num2
            entry_text.set(answer)
            operator = None # reset operator
    except ValueError:
        print('Invalid value', tempvar)

def divide():
    global num1, operator
    try:
        tempvar = entry_text.get()
        num1 = float(tempvar)  # used float() instead of int()
        entry_text.set("")
        operator = '/'   # save the operator
    except ValueError:
        print('Invalid value', tempvar)

Answer 2

The program becomes unresponsive as the while loop continues forever and never breaks, as the variable get_answer is never changed to True .

You can't click on any button, because the while loop keeps running and can't break without the condition given to it turns false or it is manually told to break after some number of loops.