往期链接：

Python项目实战

P156–L系统分形树

技术栈：随机+规则实现的分形艺术

import turtle
import random

# L系统规则
def apply_rules(axiom):
    rules = {
   
        'F': 'F[+F]F[-F]F',  # 规则
        '+': '+',             # 旋转
        '-': '-',             # 旋转
        '[': '[',             # 存储状态
        ']': ']'              # 恢复状态
    }
    return ''.join(rules.get(char, char) for char in axiom)

# 生成 L 系统字符串
def generate_l_system(axiom, iterations):
    current = axiom
    for _ in range(iterations):
        current = apply_rules(current)
    return current

# 绘制分形树
def draw_l_system(t, instructions, angle, length):
    stack = []
    for command in instructions:
        if command == 'F':
            t.forward(length)
        elif command == '+':
            t.right(angle)
        elif command == '-':
            t.left(angle)
        elif command == '[':
            stack.append((t.position(), t.heading(), t.pensize()))
            t.color(random_color())  # 随机颜色
            t.pensize(t.pensize() + 1)  # 增加线条粗细
        elif command == ']':
            position, heading, pensize = stack.pop()
            t.penup()
            t.setposition(position)
            t.setheading(heading)
            t.pensize(pensize)
            t.pendown()

# 随机颜色生成
def