title: Creating a simple gui program using Tkinter in Python
body: <p>Don't understand why this simple code doesn't work. Sorry in advance for my stupidity. I have such errors:</p>
  
  <pre><code>Traceback (most recent call last):
    File "C:/python/coding/simple_gui", line 28, in &lt;module&gt;
       app=Application(root)
    File "C:/python coding/simple_gui", line 9, in __init__
      self.create_widgets()
    File "C:/python coding/simple_gui", line 14, in create_widgets
      self.bttnl.grid()
  AttributeError: 'Application' object has no attribute 'bttnl'
  </code></pre>
  
  <p>My code is:</p>
  
  <pre><code>from tkinter import *
  
  
  class Application(Frame):
      def __init__(self, master):
          """ Initialize frame"""
          super(Application, self).__init__(master)
          self.grid()
          self.create_widgets()
      def create_widgets(self):
          """Create 3 useless buttons"""
          #first one
          self.bttn1=Button(self, text ="I do nothing!")
          self.bttnl.grid()
          #second button
          self.bttn2 = Button(self)
          self.bttn2.grid()
          self.bttn2.configure(text ="Me too!")
          #third one
          self.bttn3 = Button(self)
          self.bttn3.grid()
          self.bttn3["text"]="And me also!"
  
  root=Tk()
  #alter window
  root.title("The simpliest gui")
  root.geometry("200x100")
  app=Application(root)
  root.mainloop()
  </code></pre>