Screenshot of output image
我使用乌龟制作了一个随机行走程序，希望通过更改颜色显示两只乌龟在路径上的交叉位置。
`import turtle as T
import random as R
t = T.Turtle()
u = T.Turtle()
t.speed(0)
u.speed(0)
t.hideturtle()
u.hideturtle()
t.color("red")
u.color("blue")
def randWalk(num):
for i in range(0, num):
x = R.choice((-1,1))
X = R.choice((-1,1))
y = R.choice((-1,1))
Y = R.choice((-1,1))
t.forward(x)
u.forward(X)
if y == 1:
t.left(90)
t.forward(1)
else:
t.right(90)
t.forward(1)
if Y == 1:
u.left(90)
u.forward(1)
else:
u.right(90)
u.forward(1)
randWalk(4000)`
最佳答案
Turtle无法询问屏幕上当前使用的是哪种颜色，因此解决此问题的一种方法可能是拥有某种后备存储，您可以在其中跟踪将什么颜色写入到哪个像素。这是一个使用Python列表的粗略示例：
from turtle import Screen, Turtle
from random import choice
WIDTH, HEIGHT = 300, 300
PEN_COLORS = ['red', 'blue']
OVERLAP_COLOR = 'green'
def randWalk(number):
for _ in range(number):
for turtle in turtles:
direction = choice((-1, 1))
turtle.forward(direction)
x, y = map(round, turtle.position())
old_color = color = turtle.pencolor()
turtle.undo() # undo forward()
if grid[y][x] and grid[y][x] != color:
color = OVERLAP_COLOR
turtle.pencolor(color)
turtle.goto(x, y) # redo forward()
turtle.pencolor(old_color)
grid[y][x] = color
choice((turtle.left, turtle.right))(90)
screen.update()
screen = Screen()
screen.setup(WIDTH, HEIGHT)
screen.tracer(False)
grid = [[None] * WIDTH for _ in range(HEIGHT)]
turtles = []
for color in PEN_COLORS:
turtle = Turtle()
turtle.hideturtle()
turtle.pencolor(color)
turtles.append(turtle)
randWalk(4000)
screen.tracer(True)
screen.exitonclick()
随着乌龟在浮点平面上行走，代码中还有其他复杂性，但是我们需要将其强制到整数平面以容纳我们的后备存储并减少不良的绘图伪像。