title: AttributeError: class Tk has no attribute 'tk'
body: <p>hey guys i stuck on simple python GUI program</p>
  
  <pre><code>import Tkinter as tk
  
  window = tk.Tk
  text_box = tk.Entry(window)
  
  
  def save_text():
      str1 = text_box.get()
      fx = open("file1.txt", "w")
      fx.write(str1)
      fx.close()
  
  btn1 = tk.Button(window, text="Save", command="save_text")
  text_box.pack()
  btn1.pack()
  window.mainloop()
  </code></pre>
  
  <p>i this error:</p>
  
  <pre><code>Traceback (most recent call last):
    File "C:/Users/Saket/PycharmProjects/guiform1/firstform.py", line 5, in &lt;module&gt;
      text_box = tk.Entry(window)
    File "C:\Python27\lib\lib-tk\Tkinter.py", line 2385, in __init__
      Widget.__init__(self, master, 'entry', cnf, kw)
    File "C:\Python27\lib\lib-tk\Tkinter.py", line 1965, in __init__
      BaseWidget._setup(self, master, cnf)
    File "C:\Python27\lib\lib-tk\Tkinter.py", line 1943, in _setup
      self.tk = master.tk
  AttributeError: class Tk has no attribute 'tk'
  </code></pre>
  
  <p>Anybody having idea what am i doing wrong please help me??</p>