title: Why do I keep getting AttributeError: 'module' object has no attribute
body: <p>I am new to Python and was trying a few problems.  This one is to create a traffic light. Not sure why I keep getting this error
    AttributeError: 'module' object has no attribute 'canvas'</p>
  
  <p>Code below</p>
  
  <h1>Chapter 9 9.25</h1>
  
  <pre><code>import tkinter as tk
  
  class TrafficLight(tk.Frame):
  
      def __init__(self, parent=None):
          tk.Frame.__init__(self, parent, bg='green')
          self.grid()
  
  # create a canvas to draw on
  
  self.canvas = tk.canvas(self, width=260, height=280, bg='white')
  
  self.canvas.grid()
  
  
  self.make_widgets()
  
  
  def make_widgets(self):
      self.canvas.create_rectangle(80, 20, 170, 260)
  
  #imagine a square box
  # upper left corner coordinates x1, y1
  # lower right corner coordinates x2, y2
  # and sides of length span for each circle
  
  span = 50
  x1 = 100
  y1 = 50
  x2 = x1 + span
  y2 = y1 + span
  
  self.canvas.create_oval(x1, y1, x2, y2, fill='red')
  self.canvas.create_oval(x1, y1+70, x1, y2+70, fill='yellow')
  self.canvas.create_oval(x1, y1+140, x2, y2+140, fill='green')
  
  if __name__ == '__main__':
      light = TrafficLight()
      light.mainloop()
  </code></pre>