title: Python Turtle: Draw concentric circles using circle() method
body: <p>I was showing a grandson patterns drawn with Python's Turtle module,
  and he asked to see concentric circles.
  I thought it would be faster to use the turtle's <a href="https://docs.python.org/2/library/turtle.html#turtle.circle" rel="nofollow noreferrer"><code>circle()</code></a> to draw them
  than to write my own code for generating a circle. Ha! I am stuck. 
  I see that the circle produced begins its circumference at the turtle's
  current location and its direction of drawing depends on turtle's current
  direction of motion, but I can't figure out what I need to do to get
  concentric circles.
  I am not at this point interested in an efficient way of producing
  concentric circles: I want to see what I have to do to get
  <em>this</em> way to work:</p>
  
  <pre><code>def turtle_pos(art,posxy,lift):
      if lift:
          art.penup()
          art.setposition(posxy)
          art.pendown()
  
  def drawit(tshape,tcolor,pen_color,pen_thick,scolor,radius,mv):
      window=turtle.Screen() #Request a screen
      window.bgcolor(scolor) #Set its color
  
      #...code that defines the turtle trl
  
      for j in range(1,11):
          turtle_pos(trl,[trl.xcor()+mv,trl.ycor()-mv],1)
          trl.circle(j*radius)
  
  drawit("turtle","purple","green",4,"black",20,30)
  </code></pre>