python递归绘制分形树 python turtle画分形树 递归

分形树绘制1.0

案例描述

案例分析

程序

可以写一些print，帮助理解

树0.0：

完整程序：

"""
作者：张梦
功能：用迭代绘制分形树
版本：1.0
日期：2018.12.9
"""

"""引用turtle库"""
import turtle

"""绘制树枝"""
def draw_branch(branch_length):
    if branch_length > 5:
        # 绘制右侧树枝
        turtle.forward(branch_length)
        print('向前', branch_length)
        turtle.right(20)
        print('右转,20')
        draw_branch(branch_length-15)

        # 绘制左侧树枝
        turtle.left(40)
        print('左转,40')
        draw_branch(branch_length - 15)

        # 返回之前的树枝
        turtle.right(20)
        print('右转，20')
        turtle.backward(branch_length)
        print('返回', branch_length)

"""主函数"""
def main ():
    turtle.left(90)
    turtle.penup()
    turtle.backward(150)
    turtle.pendown()
    turtle.color('brown')
    draw_branch(100)
    turtle.exitonclick()
if __name__ =="__main__":
    main()

树1.0：

树枝末端加了颜色

程序：（只修改了子程序：draw_branch）

def draw_branch(branch_length):
    if branch_length > 5:

        # 绘制右侧树枝
        turtle.forward(branch_length)
        print('向前', branch_length)
        turtle.right(20)
        print('右转,20')
        draw_branch(branch_length-15)

        # 绘制左侧树枝
        turtle.left(40)
        print('左转,40')
        draw_branch(branch_length - 15)
        
		#树枝末端加颜色
        if branch_length <= 25:
             turtle.color('green')
        else:
             turtle.color('brown')
            
        # 返回之前的树枝
        turtle.right(20)
        print('右转，20')
        turtle.backward(branch_length)
        print('返回', branch_length)

强调：

树2.0：

枝干变得有粗有细

由于迭代的原因，画最右边的树枝，一定画到头，才会返回然后画左边的树枝，而判断语句在画左边和返回之间，所以当画完右边返回时颜色才由棕色变为绿色，覆盖住原来的棕色，画出来是对的，但这个不适用于粗细。因为已经画完粗的返回时细的是盖不住粗的，所以就有了上图效果。

程序：（只修改了子程序：draw_branch）

def draw_branch(branch_length):
    if branch_length > 5:

        # 绘制右侧树枝
        turtle.forward(branch_length)
        print('向前', branch_length)
        turtle.right(20)
        print('右转,20')
        draw_branch(branch_length-15)

        # 绘制左侧树枝
        turtle.left(40)
        print('左转,40')
        draw_branch(branch_length - 15)
        
		#树枝末端加颜色
        if branch_length <= 25:
             turtle.color('green')
        else:
             turtle.color('brown')
		#树枝变粗细
        if branch_length == 70:
             turtle.pensize(3)
        elif branch_length == 55:
             turtle.pensize(2)
        elif branch_length == 40:
             turtle.pensize(1)
        elif branch_length == 25:
             turtle.pensize(2)
        else:
              turtle.pensize(1)
              
        # 返回之前的树枝
        turtle.right(20)
        print('右转，20')
        turtle.backward(branch_length)
        print('返回', branch_length)

强调：

树3.0

所以还是老老实实画每个树枝都判断一下吧

程序：（只修改了子程序：draw_branch）

def draw_branch(branch_length):
    if branch_length > 5:

        # 绘制右侧树枝
        turtle.forward(branch_length)
        print('向前', branch_length)
        turtle.right(20)
        print('右转,20')
        if branch_length <= 25:
            turtle.color('green')
        else:
            turtle.color('brown')
        if branch_length == 100:
            turtle.pensize(5)
        elif branch_length == 85:
            turtle.pensize(4)
        elif branch_length == 70:
            turtle.pensize(3)
        elif branch_length == 55:
            turtle.pensize(2)
        else:
            turtle.pensize(1)
        draw_branch(branch_length-15)

        # 绘制左侧树枝
        turtle.left(40)
        print('左转,40')
        if branch_length <= 25:
            turtle.color('green')
        else:
            turtle.color('brown')
        if branch_length == 100:
            turtle.pensize(5)
        elif branch_length == 85:
            turtle.pensize(4)
        elif branch_length == 70:
            turtle.pensize(3)
        elif branch_length == 55:
            turtle.pensize(2)
        else:
            turtle.pensize(1)
        draw_branch(branch_length - 15)
        
        # 返回之前的树枝
        turtle.right(20)
        print('右转，20')
        if branch_length <= 25:
            turtle.color('green')
        else:
            turtle.color('brown')
        if branch_length == 100:
            turtle.pensize(5)
        elif branch_length == 85:
            turtle.pensize(4)
        elif branch_length == 70:
            turtle.pensize(3)
        elif branch_length == 55:
            turtle.pensize(2)
        else:
            turtle.pensize(1)
        turtle.backward(branch_length)
        print('返回', branch_length)

其实这里还可以把变颜色和变粗细的程序放到一个子函数里，简洁多了，但是我懒得弄了。。。