Question

I am suppose to write a program using python’s turtle that creates a tree with levels. Below are some I/O’s so you see what it is suppose to do.

My program works for the first case, but prints too many for the second case. The stipulations for this program are:

• must be recursive

• can only use the following turtle functions:

  turtle.forward(100)     <-- turtle goes forward 100 steps
  turtle.right(90)        <-- turtle turns right 90 degrees
  turtle.penup()          <-- turtle lifts its pen up off of the paper
  turtle.forward(100)     <-- turtle goes forward 100 steps
  turtle.pendown()        <-- turtle puts its pen down on the paper
  turtle.pencolor("red")  <-- turtle uses red pen
  turtle.circle(100)      <-- turtle draws circle of radius 100 
  turtle.pencolor("blue") <-- turtle changes to blue pen (most other common colors work too!)
  turtle.forward(50)      <-- turtle moves forward 50 steps
  turtle.xcor()           <-- turtle returns its current x-coordinate
  turtle.ycor()           <-- turtle returns its current y-coordinate
  

My Program:

import turtle

def tree(length,n):
    """ paints a branch of a tree with 2 smaller branches, like an Y"""
    if length < (length/n):
           return       # escape the function
    turtle.forward(length)        # paint the thik branch of the tree
    turtle.left(45)          # rotate left for smaller "fork" branch
    tree(length * 0.5,length/n)      # create a smaller branch with 1/2 the lenght of the parent branch
    turtle.right(90)         # rotoate right for smaller "fork" branch
    tree(length * 0.5,length/n)      # create second smaller branch
    turtle.left(45)          # rotate back to original heading
    turtle.backward(length)       # move back to original position
    return              # leave the function, continue with calling program

Answer 1

I think there are two problems.

First, for the recursive calls, the second parameter should be n-1 instead of length/n. If you’re drawing level n, the next call will draw level n-1, not level length/n.

The second problem is the escape condition. With the first change, the drawing will finish when there are no more levels left to draw, or n==1.

It sounds like homework, so I won’t post the exact code,.