如何使多个克隆在 python 龟中同时运行

Question

I am trying to make a code where you can press the spacebar and an object will move forwards constantly. I am hoping to be able to have multiple of these objects moving at once without having to code hundreds of them separately.

This is my current code:

Bullet:

bullet = turtle.Turtle()
bullet.speed(0)
bullet.shape("circle")
bullet.color("red")
bullet.shapesize(stretch_wid=0.5, stretch_len=0.5)
bullet.penup()
bullet.goto(-200, -200)
bullet.hideturtle()

Movement:

def shoot_bullet():
    stop = False
    bullet2 = bullet.clone()
    bullet2.showturtle()
    while stop == False:
        y = bullet2.ycor()
        bullet2.sety(y + 20)
        wn.update()
        time.sleep(0.5)
...

onkeypress(shoot_bullet, "space")

This works until I press space again and the bullet just stops as 'bullet2' has been redefined as the new bullet I create when I press space. Is there a way to create multiple clones which can run on top of each other?

Answer 1

Your while stop == False: loop and time.sleep(0.5) have no place in an event-driven environment like turtle. Instead, as we fire each bullet, the below code attaches a timer event that moves it along until it disappears. At which point the bullet is recycled.

This simplified example just shoots bullets in random directions from the center of the screen. You can keep hitting the space bar to generate simultaneous bullets that all move in their own direction until they get far enough away:

from turtle import Screen, Turtle
from random import randrange

def move_bullet(bullet):
    bullet.forward(15)

    if bullet.distance((0, 0)) > 400:
        bullet.hideturtle()
        bullets.append(bullet)
    else:
        screen.ontimer(lambda b=bullet: move_bullet(b), 50)

    screen.update()

def shoot_bullet():
    screen.onkey(None, 'space')  # disable handler inside hander

    bullet = bullets.pop() if bullets else bullet_prototype.clone()
    bullet.home()
    bullet.setheading(randrange(0, 360))
    bullet.showturtle()

    move_bullet(bullet)

    screen.onkey(shoot_bullet, 'space')  # reenable handler on exit

bullet_prototype = Turtle('circle')
bullet_prototype.hideturtle()
bullet_prototype.dot(10)  # just for this example, not for actual code
bullet_prototype.shapesize(0.5)
bullet_prototype.color('red')
bullet_prototype.penup()

bullets = []

screen = Screen()
screen.tracer(False)
screen.onkey(shoot_bullet, 'space')
screen.listen()
screen.mainloop()