title: Im doing a program on python which is a mailbox but i keep getting this error
body: <p>Im from portugal so my english might not be the best but I hope you understand.</p>
  
  <p>I have this code from my mailbox made on tkinter:</p>
  
  <pre><code>from gestor import Mensagem
  from gestor import CaixaDeCorreio
  from gestor import Utilizador
  import time
  import os
  from tkinter import*
  dic={}
  
  class window():
  
  def __init__(self,mGui):
      self.utilizadores = []
      self.passwords = []               
  
      self.textEcra=Label(mGui,text='Login na Caixa de Correio',fg='blue',font = ('Arial','15','bold')).pack()
  
      self.textNome=Label(mGui,text='Utilizador',font = ('Arial','12','normal')).pack() #(side=LEFT)
  
      self.campNome=Entry(mGui).pack()
  
      self.textPassword =Label(mGui,text='Password',font = ('Arial','12','normal')).pack() #(side=LEFT)
  
      self.campPassword = Entry(mGui,show='*').pack()
  
      self.botao1=Button(mGui,text ='Entrar',font = ('Arial','12','normal'),command = self.verificacao).place(x=80,y=160)
  
      self.botao2=Button(mGui,text ='Registar',font = ('Arial','12','normal'),command = self.registo).place(x=140,y=160)
  
  
  
  
  def verificacao(self):
      utilizador = self.campNome.get()
      '''if utilizador == "":
          messagebox.showinfo("Introduza um nome de utilizador!")
      else:
          pass'''
      password = self.campPassword.get()
      if utilizador in self.utilizadores and password in self.passwords:
          print("Acesso garantido!")
          novaMsg()   
          root.destroy()
      else:
          print("Por favor faça o resgisto!")
  
  def registo(self,*args):
      utilizador = self.campNome.get()
      self.utilizadores.append(utilizador)
      password = self.campPassword.get()
      self.passwords.append(password)
      print("Registado com sucesso!")
  
  
  mGui=Tk()
  mGui.geometry('300x300+400+300')
  mGui.title('Caixa de Correio')
  window(mGui)
  mGui.mainloop()
  </code></pre>
  
  <p>And  the windows opens and I can insert user and password but when I press  button enter this error appears:</p>
  
  <pre><code>Exception in Tkinter callback
  Traceback (most recent call last):
  File "C:\Users\rosin\AppData\Local\Programs\Python\Python35-32\lib\tkinter\__init__.py", line 1549, in __call__
  return self.func(*args)
   File "x-wingide-python-shell://86084224/2", line 50, in verificacao
  AttributeError: 'NoneType' object has no attribute 'get'
  </code></pre>
  
  <p>I have been searching on forum from similiar errors but I can't fix this one. Thanks in advance for any help. There are some portuguese words on code, please if you don't understand any post it. I will be online almost the time!</p>
  
  <p>Regards from Azorean Islands.</p>