Python 代码实现随机分形树生成 (L-系统)

以下是一段基于 L-系统生成随机分形树的 Python 代码：

import turtle
import random

# 定义 L-系统
def generate_l_system(axiom, rules, generations):
    # 初始化序列
    start_string = axiom
    # 循环生成序列
    for i in range(generations):
        # 新的序列
        end_string = ""
        # 遍历序列中的每个字符
        for char in start_string:
            # 如果字符有对应的规则，替换为规则中的字符串
            if char in rules:
                end_string += rules[char]
            else:
                end_string += char
        start_string = end_string
    return start_string

# 绘制分形树
def draw_l_system(some_turtle, instructions, angle, distance):
    # 遍历序列中的每个字符
    for cmd in instructions:
        # 如果是 F，向前移动一定距离
        if cmd == 'F':
            some_turtle.forward(distance)
        # 如果是 -，向左旋转一定角度
        elif cmd == '-':
            some_turtle.left(angle)
        # 如果是 +，向右旋转一定角度
        elif cmd == '+':
            some_turtle.right(angle)

# 设置初始参数
axiom = 'F'
rules = {'F': 'FF+[+F-F-F]-[-F+F+F]'}
generations = 5
angle = 25
distance = 5

# 生成 L-系统 序列
instructions = generate_l_system(axiom, rules, generations)

# 初始化海龟
t = turtle.Turtle()
t.speed(0)
t.left(90)
t.penup()
t.goto(0, -300)
t.pendown()

# 绘制分形树
for i in range(10):
    t.color(random.choice(['brown', 'red', 'orange']))
    t.pensize(10-i)
    draw_l_system(t, instructions, angle, distance)

# 隐藏海龟
t.hideturtle()
turtle.done()

代码注释如下：

导入 turtle 和 random 模块

import turtle
import random

定义 generate_l_system 函数，用于生成 L-系统序列

def generate_l_system(axiom, rules, generations):
    # 初始化序列
    start_string = axiom
    # 循环生成序列
    for i in range(generations):
        # 新的序列
        end_string = ""
        # 遍历序列中的每个字符
        for char in start_string:
            # 如果字符有对应的规则，替换为规则中的字符串
            if char in rules:
                end_string += rules[char]
            else:
                end_string += char
        start_string = end_string
    return start_string

定义 draw_l_system 函数，用于绘制分形树

def draw_l_system(some_turtle, instructions, angle, distance):
    # 遍历序列中的每个字符
    for cmd in instructions:
        # 如果是 F，向前移动一定距离
        if cmd == 'F':
            some_turtle.forward(distance)
        # 如果是 -，向左旋转一定角度
        elif cmd == '-':
            some_turtle.left(angle)
        # 如果是 +，向右旋转一定角度
        elif cmd == '+':
            some_turtle.right(angle)

设置初始参数

axiom = 'F'
rules = {'F': 'FF+[+F-F-F]-[-F+F+F]'}
generations = 5
angle = 25
distance = 5

生成 L-系统序列

instructions = generate_l_system(axiom, rules, generations)

初始化海龟

t = turtle.Turtle()
t.speed(0)
t.left(90)
t.penup()
t.goto(0, -300)
t.pendown()

绘制分形树

for i in range(10):
    t.color(random.choice(['brown', 'red', 'orange']))
    t.pensize(10-i)
    draw_l_system(t, instructions, angle, distance)

隐藏海龟，结束程序

t.hideturtle()
turtle.done()