1.源码实现

import matplotlib.pyplot as plt
import math

# 使用Matploitlib库, 定义自己的Turtle类
class my_turtle:
    # 构造方法, 自动执行
    def __init__(self, A):
        # 初始化实例
        self.x = A[0]
        self.y = A[1]
        self.d = A[2]

    # 获取turtle当前状态
    def get_point(self):
        return (self.x, self.y, self.d)

    # 恢复到状态p点
    def restore(self, p):
        self.x = p[0]
        self.y = p[1]
        self.d = p[2]

    # 向前一步, 画线
    def forward(self, L):
        # 计算下一点的坐标
        x1 = self.x + L*math.cos(self.d*math.pi/180)
        y1 = self.y + L*math.sin(self.d*math.pi/180)

        # 两点之间画线
        X = [self.x, x1]
        Y = [self.y, y1]

        # 绘制线段
        plt.plot(X, Y, c=p_color, alpha=1)

        # 设置当前状态为下一点的状态
        self.x = x1
        self.y = y1

    # 向前一步, 不画线
    def go(self, L):
        x1 = self.x + L*math.cos(self.d*math.pi/180)
        y1 = self.y + L*math.sin(self.d*math.pi/180)

        self.x = x1
        self.y = y1

    # 向左转angle度
    def left(self, angle):
        self.d = self.d + angle

    # 向右转angle度
    def right(self, angle):
        self.d = self.d - angle

# L系统函数, LS为图形文法结构, A为起始点, L为步长, n为迭代次数
def L_system(LS, A, L, n):
    angle = LS['angle']
    axiom = LS['axiom']
    P = LS['P']

    # 字符串重写
    i = 0
    new_str = axiom

    # 重复迭代替换, 直到达到迭代次数
    while i < n:
        s = []

        # 遍历字符串中的每个字符
        for alpha in new_str:
            k = 0

            for rule in P:
                origin, desti = rule.split('->')

                if alpha == origin:
                    if desti:
                        s.append(desti)
                    k = 1

            if k == 0:
                s.append(alpha)

        new_str = ''.join(s)

        print(new_str)

        i = i + 1

    # 实例化生成一个my_turtle对象
    t1 = my_turtle(A)

    # 解释字符串, 绘图
    stack = []

    # 遍历字符串
    for alpha in new_str:
        if alpha not in plot_V:
            continue

        if alpha == 'F':
            t1.forward(L)
        elif alpha == 'f':
            t1.go(L)
        elif alpha == '+':
            t1.left(angle)
        elif alpha == '-':
            t1.right(angle)
        elif alpha == '[':
            C = t1.get_point()
            stack.append(C)
        elif alpha == ']':
            A = stack[-1]
            del stack[-1]
            t1.restore(A)

# 定义符号的图形学解释
plot_V = {'F': 'Move forward by line length drawing a line',
    'f': 'Move forward by line length without drawing a line',
    '+': 'Turn left by turning angle',
    '-': 'Turn right by turning angle',
    '[': 'push',
    ']': 'pop',
}

# 科赫曲线图形结构
koch = {'angle': 60,
    'axiom': 'F',
    'P': ['F->F+F--F']
}

# 科赫雪花图形结构,
koch_snow = {'angle': 60,
    'axiom': 'F--F--F',
    'P': ['F->F+F--F+F']
}

# 分形龙图形结构
dragon = {'angle': 45,
    'axiom': 'FX',
    'P': ['F->', 'Y->+FX--FY+', 'X->-FX++FY-']
}

if __name__ == '__main__':
    # 指定背景颜色
    b_color = 'white'

    # 指定画笔颜色
    p_color = 'black'

    # 设置窗口的默认颜色
    plt.rcParams['figure.facecolor'] = b_color

    # 设置起始点
    A = (0, 0, 0)

    # 设置步长
    L = 30

    # 设置迭代次数
    n = 10

    # 调用L-system函数生成字符串并绘制图形
    L_system(dragon, A, L, n)

    # 设置x, y轴的单位长度相等
    plt.axis('equal')

    # 隐藏坐标轴
    plt.axis('off')

    # 保存图形为文件
    plt.savefig('1.png', facecolor=b_color)

2.运行程序

$ python3 test.py

3.运行结果

1.png