title: Why does tkinter give me an "invalid command name .37395760" error?
body: <p>I'm getting a strange error when I try to run my program. It's supposed to draw a red Circle on a TK() window.</p>
  
  <p>Here's my code:</p>
  
  <pre><code>from tkinter import *
  
  class Circle:
      def __init__(self, radius, points = 0, xcoordinate = 0, ycoordinate = 0):    
          self.radius = radius
          self.points = points
          self.color = "red"
          self.xcoordinate = xcoordinate
          self.ycoordinate = ycoordinate
  
  class World:
      def __init__(self):
          self.constructor = Tk()
          self.constructor.title("Circle")
          self.canvas = Canvas(self.constructor, width = 200, height = 200,     borderwidth = 0, highlightthickness = 0, bg = "black")
          self.canvas.grid()
          self.constructor.mainloop()
  
      def drawPlayer(self):
          player = Circle(50)
          self.canvas.create_oval(player.xcoordinate - player.radius, player.ycoordinate - player.radius, player.xcoordinate + player.radius, player.ycoordinate + player.radius, fill = player.color)
  
  c = World()
  c.drawPlayer()
  </code></pre>
  
  <p>I'm getting this error: </p>
  
  <pre><code>File "C:\Python34\Lib\tkinter\__init__.py", line 2318, in _create
      *(args + self._options(cnf, kw))))
  _tkinter.TclError: invalid command name ".37395760"
  </code></pre>
  
  <p>I've reread and even wrote down my code to see where I was going wrong, but I just can't find an error. </p>
  
  <p><strong>NOTE: This error happens after I run it and a window appears with a black canvas but no circle.</strong></p>
  
  <p>Thank you!</p>