title: In tkinter, why winfo_height() always return 1?
body: <p>This is the most easy example.</p>
  
  <pre><code>#py3
  from tkinter import *
  tk = Tk()
  canvas = Canvas(tk, width= 500 , height = 400)
  canvas.winfo_height()
  #In [4]: canvas.winfo_height()
  #Out[4]: 1
  </code></pre>