How to stop a GUI from being automatically resized?

I wrote a calculator app by using Tkinter. The problem is when I click numbers or operators etc, the whole GUI resized automatically. Actually, I think the width of the label must fix in some way. I tried to use a frame as the parent for the label but it didn’t work. Should I use a different layout manager?

Here is my code:

from tkinter import *

root = Tk()
root.title('A Simple Calculator')
#root.geometry('500x600')
root.resizable(width=False, height=False)


#Screen of the calculator
isPushed = StringVar()
#print(isPushed.get() == '')
var = StringVar()
#screenFrame = Frame(root)
screenLabel = Label(root, text='', padx=150, pady=13, bg='black',
                    fg='white', font=('Times', 15), textvariable=var)

#define commands
#numbers
def one():
    if isPushed.get() == '':
        s = var.get()
        var.set(s + '1')
    else:
        var.set('')
        var.set('1')
        isPushed.set('')
def two():
    if isPushed.get() == '':
        s = var.get()
        var.set(s + '2')
    else:
        var.set('')
        var.set('2')
        isPushed.set('')
def three():
    if isPushed.get() == '':
        s = var.get()
        var.set(s + '3')
    else:
        var.set('')
        var.set('3')
        isPushed.set('')
def four():
    if isPushed.get() == '':
        s = var.get()
        var.set(s + '4')
    else:
        var.set('')
        var.set('4')
        isPushed.set('')
def five():
    if isPushed.get() == '':
        s = var.get()
        var.set(s + '5')
    else:
        var.set('')
        var.set('5')
        isPushed.set('')
def six():
    if isPushed.get() == '':
        s = var.get()
        var.set(s + '6')
    else:
        var.set('')
        var.set('6')
        isPushed.set('')
def seven():
    if isPushed.get() == '':
        s = var.get()
        var.set(s + '7')
    else:
        var.set('')
        var.set('7')
        isPushed.set('')
def eight():
    if isPushed.get() == '':
        s = var.get()
        var.set(s + '8')
    else:
        var.set('')
        var.set('8')
        isPushed.set('')
def nine():
    if isPushed.get() == '':
        s = var.get()
        var.set(s + '9')
    else:
        var.set('')
        var.set('9')
        isPushed.set('')
def zero():
    if isPushed.get() == '':
        s = var.get()
        var.set(s + '0')
    else:
        var.set('')
        var.set('0')
        isPushed.set('')

#operations
def add():
    s = var.get()
    var.set(' {} + '.format(s))
    isPushed.set('')
def subtract():
    s = var.get()
    var.set(' {} - '.format(s))
    isPushed.set('')
def multiply():
    s = var.get()
    var.set(' {} {} '.format(s, chr(215)))
    isPushed.set('')
def divide():
    s = var.get()
    var.set(' {} {} '.format(s, chr(247)))
    isPushed.set('')
def calculate():
    isPushed.set('y')
    s = var.get()
    s = s.split()
    #exclude operands
    if '.' in s[0] or '.' in s[2]:
        x = float(s[0])
        y = float(s[2])
    else:
        x = int(s[0])
        y = int(s[2])
    #make the operation
    if s[1] == '+':
        var.set(x + y)
    elif s[1] == '-':
        var.set(x - y)
    elif s[1] == chr(215):
        var.set(x * y)
    else:
        var.set(x / y if x % y != 0 else x // y)



#functional Buttons
def clean():
    var.set('')
def decimal_point():
    s = var.get()
    var.set('{}.'.format(s))

    


#define Buttons
#numbers
num_1 = Button(root, text='1', font=('Times', 20), command=one)
num_2 = Button(root, text='2', font=('Times', 20), command=two)
num_3 = Button(root, text='3', font=('Times', 20), command=three)
num_4 = Button(root, text='4', font=('Times', 20), command=four)
num_5 = Button(root, text='5', font=('Times', 20), command=five)
num_6 = Button(root, text='6', font=('Times', 20), command=six)
num_7 = Button(root, text='7', font=('Times', 20), command=seven)
num_8 = Button(root, text='8', font=('Times', 20), command=eight)
num_9 = Button(root, text='9', font=('Times', 20), command=nine)
num_0 = Button(root, text='0', font=('Times', 20), command=zero)

#operations
addition = Button(root, text='+', font=('Times', 20), command=add)
subtraction = Button(root, text='-', font=('Times', 20), command=subtract)
multiplication = Button(root, text=chr(215), font=('Times', 20), command=multiply)
division = Button(root, text=chr(247), font=('Times', 20), command=divide)
equal = Button(root, text='=', font=('Times', 20), command=calculate)

#functional Buttons
clear = Button(root, text='C', font=('Times', 20), command=clean)
period = Button(root, text='.', font=('Times', 20), command=decimal_point)

#Packing Buttons into the form
#Screen of the calculator
#screenFrame.grid(row=0, column=0, columnspan=4, sticky=W+E)
#screenLabel.pack()
screenLabel.grid(row=0, column=0, columnspan=4, sticky=W+E)

#numbers
num_1.grid(row=1, column=0, sticky=W+E)
num_2.grid(row=1, column=1, sticky=W+E)
num_3.grid(row=1, column=2, sticky=W+E)

num_4.grid(row=2, column=0, sticky=W+E)
num_5.grid(row=2, column=1, sticky=W+E)
num_6.grid(row=2, column=2, sticky=W+E)

num_7.grid(row=3, column=0, sticky=W+E)
num_8.grid(row=3, column=1, sticky=W+E)
num_9.grid(row=3, column=2, sticky=W+E)

num_0.grid(row=4, column=0, columnspan=2, sticky=W+E)

#operations
addition.grid(row=1, column=3, sticky=W+E)
subtraction.grid(row=2, column=3, sticky=W+E)
multiplication.grid(row=3, column=3, sticky=W+E)
division.grid(row=4, column=3, sticky=W+E)
equal.grid(row=5, column=3, sticky=W+E)

#functional Buttons
clear.grid(row=5, column=0, columnspan=3, sticky=W+E)
period.grid(row=4, column=2, sticky=W+E)




root.mainloop()

Answer

The widget is resizing because you don’t give the widget an explicit size, so it grows to fit its contents. That is its defined behavior. Instead, you should specify the size that you want it to be. When you do that, it won’t grow when you add more characters to it than will fit.

screenLabel = Label(root, text='', pady=13, bg='black', width=20,
                    fg='white', font=('Times', 15), textvariable=var)