title: How would I modify/add text to a tkinter.Label?
body: <p>I am in the process of learning basic Python. I am currently attempting to create a simple calculator program that only has addition and subtraction. I have one issue though. I am not sure how I would add text to my Python label upon button press. Right now, upon pressing the '1' button, my program will change the display label to the text "1". However, I want my program to add text, not set it.</p>
  
  <p>For example, if I press 'button 1' 5 times, it currently will reset the label text 5 times and will result with a single 1. I want it to add the number to the label upon press, not replace.</p>
  
  <p>Current Result after pressing button 5 times: <strong>1</strong><br>
  Requested result after pressing button 5 times: <strong>11111</strong></p>
  
  <p>Here is my current code for the program. If anything is unclear, just ask; thanks.</p>
  
  <pre><code>from tkinter import *
  
  window = Tk()
  
  # Creating main label
  display = Label(window, text="")
  display.grid(row=0, columnspan=3)
  
  def add_one():
      display.config(text='1')
  
  # Creating all number buttons
  one = Button(window, text="1", height=10, width=10, command=add_one)
  two = Button(window, text="2", height=10, width=10)
  three = Button(window, text="3", height=10, width=10)
  four = Button(window, text="4", height=10, width=10)
  five = Button(window, text="5", height=10, width=10)
  six = Button(window, text="6", height=10, width=10)
  seven = Button(window, text="7", height=10, width=10)
  eight = Button(window, text="8", height=10, width=10)
  nine = Button(window, text="9", height=10, width=10)
  zero = Button(window, text="0", height=10, width=10)
  
  # Placing all number buttons
  one.grid(row=1, column=0)
  two.grid(row=1, column=1)
  three.grid(row=1, column=2)
  four.grid(row=2, column=0)
  five.grid(row=2, column=1)
  six.grid(row=2, column=2)
  seven.grid(row=3, column=0)
  eight.grid(row=3, column=1)
  nine.grid(row=3, column=2)
  
  # Creating all other buttons
  add = Button(window, text="+", height=10, width=10)
  subtract = Button(window, text="-", height=10, width=10)
  equal = Button(window, text="=", height=10, width=10)
  
  # Placing all other buttons
  add.grid(row=4, column=0)
  subtract.grid(row=4, column=1)
  equal.grid(row=4, column=2)
  
  window.mainloop()
  </code></pre>