Python Turtle 递归树

Question

我想用 python 的 turtle 编写一个程序来创建一个有层次的树。下面是一些 I/O，以便您了解它应该做什么。

我的程序适用于第一种情况，但对于第二种情况打印太多。该程序的规定是:

• 必须是递归的

• 只能使用以下 turtle 函数:

  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
  

我的程序:

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

我认为有两个问题。

首先，对于递归调用，第二个参数应该是 n-1 而不是 length/n。如果您正在绘制第 n 层，则下一次调用将绘制第 n-1 层，而不是第 n 层。

第二个问题是转义条件。对于第一个更改，绘图将在没有更多级别可供绘制时完成，或者 n==1。

这听起来像是作业，所以我不会发布确切的代码。