如何使用 python Turtle 包绘制虚线圆

Question

类似于所附图片的东西。我尝试修改我上网的代码。但我的代码进入无限循环 [1]：https://i.stack.imgur.com/HfKog.png

def draw_circle(radius):
    turtle.up()
    turtle.goto(0, radius)  # go to (0, radius)
    turtle.pendown()  # pen down
    times_y_crossed = 0
    x_sign = 1.0
    while times_y_crossed <= 1:
        turtle.dot(5, "Red")
        turtle.forward(5)  # move by 1/360
        turtle.right(1.0)
        turtle.penup()
        turtle.forward(5)  # move by 1/360
        turtle.right(1.0)
        x_sign_new = math.copysign(1, turtle.xcor())
        if x_sign_new != x_sign:
            times_y_crossed += 10
        x_sign = x_sign_new
    turtle.up()  # pen up
    return

Answer 1

您的代码存在一些问题，例如它不计入半径并且未设置笔的颜色，并且我检查过它为我做了半圈。 我向您展示了一个简单的工作示例，首先是一个虚线版本，因为您的原始代码看起来像您想要一个虚线圆圈

import turtle
import math
def draw_circle_dashed(radius):
    turtle.up()
    turtle.goto(0, radius)  # go to (0, radius)
    times_y_crossed = 0
    dist=2*math.pi*radius/360
    turtle.pencolor("red")
    for _ in range(180):
        turtle.pendown()
        turtle.forward(dist)  # move by 1/360
        turtle.right(1.0)
        turtle.penup()
        turtle.forward(dist)  # move by 1/360
        turtle.right(1.0)
    turtle.up()  # pen up
    return
draw_circle_dashed(200)

还有一个虚线变体，因为问题标题

import turtle
import math
def draw_circle_dotted(radius):
    turtle.up()
    turtle.goto(0, radius)  # go to (0, radius)
    dist=2*math.pi*radius/360
    for _ in range(360):
        turtle.dot(2,"red")
        turtle.forward(dist)  # move by 1/360
        turtle.right(1.0)
    turtle.up()  # pen up
    return
draw_circle_dotted(300)

Answer 2

我们可以使用turtle自己的circle()方法来做这个，因为我们可以任意启动和停止它，像我们一样留下点：

from turtle import Screen, Turtle
from math import pi

DOT_DIAMETER = 5

def draw_circle(radius):
    turtle.penup()

    circumference = 2 * pi * radius

    dot_extent = 360 * DOT_DIAMETER*2 / circumference  # diameter to angle

    extent = 0
    while extent < 360:
        turtle.dot(DOT_DIAMETER)
        turtle.circle(radius, extent=dot_extent)

        extent += dot_extent

screen = Screen()

turtle = Turtle()
turtle.color('red')

draw_circle(100)

turtle.hideturtle()
screen.exitonclick()

利用我们从该练习中学到的知识，现在让我们修复您的代码。我看到的问题是这样的：

turtle.right(1.0)

转向的角度取决于点的直径，但我们实际上必须计算它：

from turtle import Screen, Turtle
from math import pi, copysign

DOT_DIAMETER = 5

def draw_circle(radius):
    turtle.penup()
    turtle.sety(radius)

    diameter = 2 * radius
    circumference = pi * diameter
    dot_extent = 360 * DOT_DIAMETER / circumference  # diameter to angle

    times_y_crossed = 0
    x_sign = 1

    while times_y_crossed < 2:
        turtle.dot(DOT_DIAMETER, 'red')  # draw the dot
        turtle.right(dot_extent)
        turtle.forward(DOT_DIAMETER)

        turtle.right(dot_extent)  # draw the gap
        turtle.forward(DOT_DIAMETER)

        x_sign_new = copysign(1, turtle.xcor())

        if x_sign_new != x_sign:
            times_y_crossed += 1
            x_sign = x_sign_new

    turtle.pendown()

screen = Screen()

turtle = Turtle()
turtle.color('red')

draw_circle(100)

turtle.hideturtle()
screen.exitonclick()

通过不计算角度，并使用 1.0 的固定角度，您偏离了两倍。