title: How to update a label in Tkinter, StringVar() not working
body: <p>I am working on this short code that compares the single characters of two strings. After the first running, when I change the strings in the entryBoxes,I would like to replace the label created before, instead of creating a new one. I have already tried with StringVar() but it seems not working. (If it can be useful I'm using Python 2.7.6). Could you please give me a hint?</p>
  
  <pre><code>from Tkinter import *
  
  app = Tk()
  app.geometry('450x300')
  
  
  labelTF = Label(app, text="Insert sequence of TF").pack()
  eTF = Entry(app, width=50)
  eTF.pack()
  eTF.focus_set()
  
  
  labelSpazio = Label(app, text="\n").pack()
  
  labelResultedSequence = Label(app, text="Insert sequence of ResultedSequence").pack()
  eResultedSequence = Entry(app, width=50)
  eResultedSequence.pack()
  eResultedSequence.focus_set()
  
  def prova():
      count = 0
      uno = eTF.get().lower()
      due = eResultedSequence.get().lower()
      if len(uno)==len(due):
              for i in range(0,len(uno)):
                  if uno[i] == due[i]:
                      if uno[i] in ("a", "c","g","t"):
                          count = count + 1 
                  if uno[i] == "r" and due[i] in ("a", "g"):
                      count = count + 1 
                  if uno[i] == "y" and due[i] in ("t", "c"):
                      count = count + 1 
              percentage = int(float(count)/float(len(uno))*100)
              labelSpazio = Label(app, text="\n").pack()
              mlabel3=Label(app,text= "The final similarity percentage is: "+(str(percentage) + " %")).pack()
  
      if len(uno)!=len(due):
          mlabel2 = Label(app,text="The length of the sequences should be the same").pack()
  
  
  
  b = Button(app, text="get", width=10, command=prova)
  b.pack()
  
  mainloop()
  </code></pre>