python turtle 画树

绘制过程：

    画右子树

    返回节点

    画左子树

    返回节点

树图结果：

from turtle import *

def draw_tree(length):
    if length >= 5:
        # draw trunk of length
        forward(length)
        # turn right 20 degree
        right(20)
        # draw right child tree, child tree with length (length-10)
        draw_tree(length - 10)
        # turn left 40 degree
        left(40)
        # draw left child tree
        draw_tree(length-10)
        # turn right 20 degree
        right(20)
        # return initial position
        backward(length)

def main():
    # set color
    color('green')
    # set turtle speed, 0 is the fastest 1->10 from slow to fast
    speed(0)

    # adjust initial position of the tree
    left(90)
    penup()
    backward(150)
    pendown()

    # draw tree
    draw_tree(80)
    exitonclick()

if __name__ == '__main__':
    main()

下面我们画一个具有随机枝条长度的树，每次执行的结果都不一定一样：

具体代码如下：

from turtle import *
from random import randint

def random_delta_branch(start=6, end=15):
    return randint(start, end)

def draw_tree(trunk_length, smallest_branch):
    delta_branch = random_delta_branch()
    if trunk_length >= smallest_branch:
        forward(trunk_length)
        right(20)
        draw_tree(trunk_length - delta_branch, smallest_branch)
        left(40)
        draw_tree(trunk_length - delta_branch, smallest_branch)
        right(20)
        backward(trunk_length)


def main():
    # set color
    color('green')
    # set turtle speed, 0 is the fastest 1->10 from slow to fast
    speed(0)

    # adjust initial position of the tree
    left(90)
    penup()
    backward(150)
    pendown()

    # draw tree
    draw_tree(80, 5)
    exitonclick()

if __name__ == '__main__':
    main()