title: python tkinter update content of a label when a file is opened
body: <p>I'm currently programming a GUI using tkinter and Python 3.
  My problem here is i made a Label with which i want to display the path of a file i opened via the <code>askopenfilename()</code> method and this path is not "generated" when i start the program, obviously, so the Label is empty which makes sense but i don't know how to fix it.
  I'm gonna put the needed code below (I'm going to cut unnecessary code for this question):</p>
  
  <pre><code>import tkinter as tk
  
  class Graphicaluserinterface(tk.Frame):
  
      def __init__(self,master=None):
          super().__init__(master)
          self.grid()
          self.fileopenname=tk.StringVar()
          self.menubar = tk.Menu(self)
          self.create_widgets()
  
      def create_widgets(self):
          self.inputpathdisplay = tk.Label(self,textvariable=self.fileopenname,bg="white",width=30)
          self.inputpathdisplay.grid(row=1,column=8,columnspan=3,sticky = "W")
      def fileopening(self):
          from tkinter.filedialog import askopenfilename
          self.fileopenname = askopenfilename(filetypes = [("binary files","*.bin*"),("all files","*.*")])
  
  
  root = tk.Tk()
  app = Graphicaluserinterface(master=root)
  root.config(menu=app.menubar)
  app.mainloop()
  </code></pre>
  
  <p>I read about using <code>update_idletasks()</code>. If this is correct in my case how would i go about implementing it here?</p>