Python Turtle collision with screen boundaries

Question

How do I make the collision? so the turtle/snake doesn't go out of the box. I'm trying to make them stay inside the (-200, -200) and (200, 200).

from turtle import *
from random import *

def bounding_box():
    up()
    right(90)
    forward(200)
    down()
    left(90)
    forward(200)
    left(90)
    forward(400)
    left(90)
    forward(400)
    left(90)
    forward(400)
    left(90)
    forward(200)
    up()
    goto(0,0)
    down()

def drawSnakeRec(segments, length):
    if segments <= 0 or length <= 0:
        return 0
    else:
        color(random(), random(), random())
        forward(length)
        pensize(randint(1,10))
        left(randint(-30, 30))
        return length + drawSnakeRec(segments - 1, randint(1,20))

def drawSnakeIter(segments, length):
    TL = 0
    while segments > 0:
        color(random(), random(), random())
        pensize(randint(1,10))
        forward(length)
        left(randint(-30, 30))
        TL += length
        segments -=1
    return TL


def main():
    segments = int(input("Enter the segments between 0 and 500: "))

    bounding_box()

    hideturtle()
    speed('fast')
    
    if segments < 0 or segments > 500:
        print("Segments is out of range. Segment must be between 0 and 500 inclusive")
        input("Press enter to close")
    else:
        
        x = drawSnakeRec(segments, randint(1, 20))
        print("Recursive Snake's Length is:",x,"Units")
        input("Press Enter to go on Iterative Snake")
        up()
        goto(0,0)
        reset()
        bounding_box()
        y = drawSnakeIter(segments, randint(1,20))
        print("Iterative Snake's Length is:",y," Units")
        input("Press Enter to exit...")
        bye()
main()

What do you want to happen when it hits the edge? Coolest Turtle program I've seen, btw. — Veedrac, Sep 24 '13 at 21:30
Is this a homework assignment? If so, you really should clarify that in your question. Stackoverflow can give you pointers, but asking for any more than that is unethical and cheating. There's no magic command in turtle to help you do what you want... you've got to check where each recursion step / iteration is relative to the box yourself. — accidental_PhD, Sep 24 '13 at 21:34
@yasashiku yes this is a hw. Also, how would this be cheating since I need help how to do this. I have no idea where to start off with. — Singh2013, Sep 24 '13 at 21:39
@Veedrac thanks. I wanted to bounce off the wall and continuing drawing. — Singh2013, Sep 24 '13 at 21:41
You need to clarify that it's homework and you only want high level pointers - the way it's worded now, it implies you want someone to solve it for you. Which would be cheating. I suggest editing your question to emphasize this. — accidental_PhD, Sep 24 '13 at 21:42
@yasashiku Okay, I added that this is my Lab Homework. I never used pointers before or something like that. I have learned turtle function that is all. — Singh2013, Sep 24 '13 at 21:46
@Singh Please specify what you want to happen when the snake hits the edge of the box. There are several things you can do upon a collision event. — Shashank, Sep 24 '13 at 21:47
@ShashankGupta I got it now. THanks tho. I used position and if statement to prevent the drawing to go out of the box. — Singh2013, Sep 24 '13 at 23:16

score 1 · Answer 1 · edited Apr 02 '16 at 12:30

1

I suggest a large if like:

if turtle.ycor() >= 200 or turtle.ycor() <=-200 or  turtle.xcor() >= 200 or turtle.xcor <= -200

This worked for me!

edited Apr 02 '16 at 12:30

Tunaki

132,869
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answered Apr 02 '16 at 12:27

E1247L

13
4

score 0 · Accepted Answer · answered Sep 24 '13 at 21:47

In both the recursive version and the iterative version, you're turning a random direction and moving forward a random length. If you want to avoid the bounding box, these numbers need to know that the bounding box is there.

There are few things you could do, depending on the kind of behavior you want. Probably the easiest would be to put in a check if the new coordinate is outside of the box, and if so, change course appropriately.

If you want it to gradually avoid the box, you could factor in the distance to the nearest edge in either the turning or moving decisions.

In either case, turtle.pos() will be helpful.

thanks for the tip. I used setposition() and if statement I got it now. Thanks! — Singh2013, Sep 24 '13 at 22:27

Python Turtle collision with screen boundaries

2 Answers2