title: Changing position of cursor in Entry widget
body: <p>I am trying to shift the cursor of an Entry widget to the left, upon pressing the button. With what I've tried I can get the cursor's current position, but I can't move it.<br>
  I  searched online but I didn't find anything useful. How can I move the cursor position in an Entry widget?</p>
  
  <pre><code>#! /usr/bin/python
  from Tkinter import *
  
  class App(Frame):
      def __init__(self,parent):
          Frame.__init__(self,parent)
          self.parent=parent
          self.button = Button(self.parent, text="Shift_cursor_left", fg="red")
          self.button.pack(side=LEFT)
          self.entry_label=Entry(self.parent,width=10,bd="1",bg="cyan",font=("Helvetica",15),text="python",justify=RIGHT)
          self.entry_label.pack()
          self.entry_label.focus()
          self.entry_label.insert(0,"Python")
  
          self.button["command"]=self.shift_cursor()
  
      def shift_cursor(self):
          position = self.entry_label.index(INSERT)
          print position
          # self.entry_label.mark_set(INSERT,'1.2')
  
  root=Tk()
  app=App(root)
  root.mainloop()
  </code></pre>