阻止 Turtle 中的 `extent` 参数改变圆的方向

Question

我正在做家庭作业，其中的说明是：

Using Turtle graphics, implement function planets(), which will simulate the planetary motion of Mercury, Venus, Earth, and Mars during one rotation of planet Mars. You can assume that:

At the beginning of the simulation, all planets are lined up (say along the negative y-axis).

The distances of Mercury, Venus, Earth, and Mars from the Sun (the center of rotation) are 58, 108, 150, and 228 pixels.

For every 1 degree circular motion of Mars, Earth, Venus, and Mercury will move 2, 3, and 7.5 degrees, respectively.

The figure below shows the state of the simulation when Earth is about a quarter of the way around the Sun. Note that Mercury has almost completed its first rotation.

我得到的输出是：

这是我的代码：

import turtle
import math


s = turtle.Screen()
t = turtle.Turtle()

def jump(t,x,y):
    'makes turtle t jump to coordinates (x,y)'
    t.penup()
    t.goto(x,y)
    t.pendown()

def planets(t):

    #mercury
    jump(t,0,-58)
    t.circle(58,337.5)

    #venus
    jump(t,0,-108)
    t.circle(108,135)

#   earth
    jump(t,0,-150)
    t.circle(150,90)

#   mars
    jump(t,0,-228)
    t.circle(228,45)



planets(t)
turtle.done()

基本上，方向正在改变。如何获得所需的输出？如何阻止 extent 参数改变圆的方向？

Answer 1

问题不在于 circle() 的 extent 论点，而是你开始每一个新的轨道时，乌龟在完成前一个轨道时处于任意方向。在绘制每个轨道之前，您需要将海龟设置为已知方向：

from turtle import Screen, Turtle

def jump(t, x, y):
    ''' makes turtle t jump to coordinates (x, y) '''

    t.penup()
    t.goto(x, y)
    t.pendown()

def planets(t):

    # mercury
    t.setheading(0)
    jump(t, 0, -58)
    t.circle(58, 337.5)
    t.stamp()

    # venus
    t.setheading(0)
    jump(t, 0, -108)
    t.circle(108, 135)
    t.stamp()

    # earth
    t.setheading(0)
    jump(t, 0, -150)
    t.circle(150, 90)
    t.stamp()

    # mars
    t.setheading(0)
    jump(t, 0, -228)
    t.circle(228, 45)
    t.stamp()

turtle = Turtle()
turtle.shape('circle')
turtle.shapesize(0.5)
turtle.hideturtle()

planets(turtle)

screen = Screen()
screen.exitonclick()

阻止 Turtle 中的 `extent` 参数改变圆的方向

Stop the `extent` argument in Turtle from changing direction of circle

python

turtle-graphics

python-3.x

python-turtle