How to set screen boundaries python turtle

Question

How do I set screen boundaries so when the turtle reaches the edge it will stop or turn around

import turtle
t=turtle.Turtle()
s=turtle.Screen()
p=t.xcor()
p1=t.ycor()
x=300
y=300
s.setup(x,y)
t.color("white")
s.bgcolor("black")
def up():
 player=False
 while player==False:
 t.speed(1)
 t.fd(10)
def right():
 t.speed(0)
 t.right(90)
def left():
 t.speed(0)
 t.left(90)
s.onkey(up,"up")
s.onkey(right,"right") 
s.onkey(left,"left")
s.listen()

I thought this would stop it at the edge of the screen
The code below isn't completely done but I didn't know what to change it to

while p and p1 != x and y:
 t.right(90)
 if p and p1 == x and y:
 t.speed(0)
 t.right(180)

• furas: in other graphic systems/modules when you have to move 100pixels then you do: move few pixel (ie. 2 pixels), check collisions (ie. with screen border), move few pixel again, check collisions again, etc. - so you run it in loop.

Answer 1

I'm surprised your code works as 'up' isn't recognized as a valid keysym on my turtle system -- it has to be capitalized: 'Up'. Perhaps it's a Unix / Windows schism.

Rather than move one or two pixels at a time testing if you crossed the boundary, here's another approach. Move forward a reasonable amount, detect when you've crossed the boundary, undo that movement forward, turn around, redo your movement forward:

from turtle import Turtle, Screen
WIDTH, HEIGHT = 500, 500
DISTANCE = 10
screen = Screen()
screen.setup(WIDTH, HEIGHT)
screen.bgcolor('black')
turtle = Turtle()
turtle.speed('fastest')
turtle.color('white')
def up():
 turtle.forward(DISTANCE) # try first and undo on error
 x, y = turtle.position()
 if not -WIDTH / 2 < x < WIDTH / 2 or not -HEIGHT / 2 < y < HEIGHT / 2:
 turtle.undo() # undo error
 turtle.left(180) # turn around
 turtle.forward(10) # redo movement but in new direction
def right():
 turtle.right(90)
def left():
 turtle.left(90)
screen.onkey(up, 'Up')
screen.onkey(right, 'Right')
screen.onkey(left, 'Left')
screen.listen()
screen.mainloop()

If you add any other movement functions, e.g. Down for moving backward, then move the boundary crossing logic into its own function and share that with all the movement commands.

Answer 2

Like furas said you'll need to move a couple pixels at a time in a loop and check for collision. I needed a similar function recently, here it is if you want to try it. I've never used python turtle.screen but I'm sure you could define the edges in a list, because I used this code in a for loop of lines it shouldn't touch.

def online(point,edge):
 first = edge[0]
 second = edge[1]
 firstx = first[0]
 firsty = first[1]
 secondx = second[0]
 secondy = second[1]
 if firstx <= point[0] <= secondx and firsty >= point[1] >= secondy:
 return(True)
 elif firstx <= point[0] <= secondx and firsty <= point[1] <= secondy:
 return(True)
 elif firstx >= point[0] >= secondx and firsty >= point[1] >= secondy:
 return(True)