title: Referenced before assignment - tkinter
body: <p>I'm not sure why I get an error message when I click on get button. I've moved things around and I still get this error message.</p>
  
  <pre><code>Exception in Tkinter callback
  Traceback (most recent call last):
    File "/usr/lib/python3.4/tkinter/__init__.py", line 1536, in __call__
       return self.func(*args)
    File "address.py", line 5, in getName
       first_name = first_name.get()
  UnboundLocalError: local variable 'first_name' referenced before assignment
  </code></pre>
  
  <p>Code:</p>
  
  <pre><code>from tkinter import *
  from tkinter import ttk
  
  def getName(event):
      first_name = first_name.get()
      fieldEntry.insert(0, first_name)
  
  root = Tk()
  root.title('Address Book')
  Label(root, text='First Name').grid(row=0, sticky=W, padx=4)
  first_name = Entry(root).grid(row=0, column=1, sticky=E, pady=4)
  
  Label(root, text='Last Name').grid(row=1, sticky=W, padx=4)
  last_name = Entry(root).grid(row=1, column=1, sticky=E, pady=4)
  
  #Button(root, text='Submit').grid(row=3)
  
  getNameButton = Button(root, text='Get')
  getNameButton.bind('&lt;Button-1&gt;', getName)
  getNameButton.grid(row=3, column=1, sticky=E)
  
  
  fieldEntry = Entry(root)
  fieldEntry.grid(row=4, column=1, sticky=E)
  
  root.mainloop()
  </code></pre>