4.8. A Few More turtle Methods and Observations¶

Here are a few more things that you might find useful as you write programs that use turtles.

• Turtle methods can use negative angles or distances. So turtle.forward(-100) will move the turtle backwards, and turtle.left(-30) turns it to the right. Additionally, because there are 360 degrees in a circle, turning 30 to the left will leave you facing in the same direction as turning 330 to the right! (The on-screen animation will differ, though — you will be able to tell if tess is turning clockwise or counter-clockwise!)

  This suggests that we don’t need both a left and a right turn method — we could be minimalists, and just have one method. There is also a backward method. (If you are very nerdy, you might enjoy saying turtle.backward(-100) to move the turtle forward!)

  Part of thinking like a scientist is to understand more of the structure and rich relationships in your field. So reviewing a few basic facts about geometry and number lines, like we’ve done here is a good start if we’re going to play with turtles.

• A turtle’s pen can be picked up or put down. This allows us to move a turtle to a different place without drawing a line. The methods are penup and pendown.

  turtle.penup()
  turtle.forward(100.0)     # this moves the turtle, but no line is drawn
  turtle.down()
  

• You can speed up or slow down the turtle’s animation speed. (Animation controls how quickly the turtle turns and moves forward). Speed settings can be set between 1 (slowest) to 10 (fastest). But if you set the speed to 0, it has a special meaning — turn off animation and go as fast as possible.

  turtle.speed(10)