如何在 Python 中将 20 只海龟放在一个圆圈上？ [关闭]

Question

我必须把 20 只海龟放在一个有 20 条边的多边形的顶点上，所以它们会在一个有规则间距的圆上。

我有 Turtle 类，我想把这 20 只乌龟放在哪里。我知道如何将更多海龟放在一个文件中，但如何将它们放在一个圆圈中？

# Already working
class Turtle:

    def __init__(self, x, y):
        self.x = x
        self.y = y
        self.heading = 0
        self.lines = []

    def left(self, angle):
        self.heading -= angle

    def right(self, angle):
        self.heading += angle

    def forward(self, d):
        nx = self.x + d * math.cos(self.heading * math.pi / 180)
        ny = self.y + d * math.sin(self.heading * math.pi / 180)
        self.lines.append((self.x, self.y, nx, ny))
        self.x, self.y = nx, ny

    def save(filename, lines):
        f = open(filename, "w")
        f.write('<svg viewBox="-500 -500 1000 1000">')
        s = '<line x1="{}" y1="{}" x2="{}" y2="{}" style="{}" />'
        for i in lines:
            for x1, y1, x2, y2 in i:
                f.write(s.format(x1, y1, x2, y2, "stroke:black;stroke-width:1"))
        f.write("</svg>")
        f.close()

    # Here is just a try to put more turtles with more lines in one file
    # But I can't do this with 20 turtles...
    def set_turtles():
        global all_lines
        turtle_names = []
        t_red = Turtle(-100, 0)
        turtle_names.append(t_red)
        t1 = Turtle(0, 100)
        turtle_names.append(t1)
        t2 = Turtle(0, -100)
        turtle_names.append(t2)
        for turtle in turtle_names:
            for i in range(4):
                turtle.forward(10)
                turtle.left(90)
            all_lines.append(turtle.lines)
        save("drawing_one.html", all_lines)
        f.close()

Answer 1

与其用自定义的海龟类做所有事情，不如使用 Python 的海龟类来帮助解决问题。我们仍然需要我们自己的自定义海龟类（不称为Turtle），它可以记录它在调用foward() 时生成的行。另外实现一个静态方法将所有自定义海龟绘制的所有线条转储到 SVG 文件。但是我们可以简单地继承所有其他方法！

使用这种方法，记录线，我们不需要三角函数，而是在调用super().forward(...)之前记录乌龟的位置，然后记录乌龟的位置。

最后，我们不需要跟踪我们的自定义海龟，而是使用Screen().turtles() 并过滤掉那些不是我们自定义类的实例。

from turtle import Screen, Turtle

RADIUS = 100

class SVG_Turtle(Turtle):
    TEMPLATE = '<line x1="{}" y1="{}" x2="{}" y2="{}" style="{}" />'
    STYLE = 'stroke:black;stroke-width:1'
    HEADER = '<svg viewBox="-500 -500 1000 1000">'
    FOOTER = '</svg>'

    def __init__(self, position):
        super().__init__(visible=False)
        self.lines = []

        self.penup()
        self.goto(position)

    def forward(self, distance):
        position = self.position()
        super().forward(distance)
        self.lines.append((position, self.position()))

    @staticmethod
    def save(filename):
        with open(filename, 'w') as file:
            file.write(SVG_Turtle.HEADER)

            for turtle in screen.turtles():
                if not isinstance(turtle, SVG_Turtle):
                    continue

                for ((x1, y1), (x2, y2)) in turtle.lines:
                    file.write(SVG_Turtle.TEMPLATE.format(x1, y1, x2, y2, SVG_Turtle.STYLE))

            file.write(SVG_Turtle.FOOTER)

screen = Screen()
yertle = Turtle(visible=False)  # standard Python turtle to lay down our custom ones
yertle.penup()
yertle.sety(-RADIUS)

screen.tracer(False)

for _ in range(20):
    turtle = SVG_Turtle(yertle.position())
    turtle.setheading(turtle.towards(0, 0))  # Optional visual detail I added
    yertle.circle(RADIUS, 360 / 20, 20)

for turtle in screen.turtles():
    if isinstance(turtle, SVG_Turtle):
        for _ in range(4):
            turtle.forward(10)
            turtle.left(90)

screen.tracer(True)

SVG_Turtle.save("drawing.html")

即使您不被允许使用 Python 的海龟来帮助解决您自己的海龟问题，这也应该可以为您提供一些关于如何继续以及如何组织代码的想法。