Python: How To Make A Turtle Never Cross Over A Line

I'm trying to write a python program that will make a turtle either move forward, turn left and then move, or turn right and then move randomly without ever crossing over its own p

Solution 1:

Below is my attempt to solve your autonomous turtle problem. I chose a set() to track visited positions but also coerced the turtle onto a grid to make sure that only a limited set of points could be visited. I didn't like your approach of doing a 180 when you hit a wall as that just makes you retrace your path and fail -- instead my turtle tries to avoid hitting the walls.

I use an invisible turtle clone to "test the waters" to see if a move is good or bad. If there are no good moves, it gives up, resets, and starts again. You have to close the window to kill the program:

import turtle
from random import shuffle

WIDTH, HEIGHT = 600, 500

INCREMENT = 50

TURTLE_WIDTH = 20

X, Y = 0, 1

def dot_round(x, base=INCREMENT):
    returnint(base * round(float(x) / base))

turtle.setup(WIDTH, HEIGHT)

turtle.shape("turtle")

whileTrue:
    positions = set()

    whileTrue:

        position = (dot_round(turtle.xcor()), dot_round(turtle.ycor()))  # coerce position to gridif position in positions:
            break# collision with line

        positions.add(position)

        turtle.setposition(position)  # coerce turtle back onto our grid

        moves = list(range(3))

        shuffle(moves)

        clone = None

        for move in moves:
            clone = turtle.clone()  # use an invisible clone to test the watersclone.hideturtle()
            clone.penup()

            if move == 1:
                clone.right(90)
            elif move == 2:
                clone.left(90)

            clone.forward(INCREMENT)

            position = (dot_round(clone.xcor()), dot_round(clone.ycor()))

            if position[X] <= TURTLE_WIDTH//2 - WIDTH//2 or position[X] > WIDTH//2 - TURTLE_WIDTH//2:continue# avoid collision with wallif position[Y] <= TURTLE_WIDTH//2 - HEIGHT//2 or position[Y] > HEIGHT//2 - TURTLE_WIDTH//2:continue# avoid collision with wallif position not in positions:
                breakelse:  # no breakbreak# accept the inevitable, there's no good move

        turtle.setheading(clone.heading())
        turtle.forward(INCREMENT)

    turtle.reset()

# close the turtle window to get out of this program

This turtle only looks one move ahead -- he easily gets himself into jams he can't get himself out of.

This hopefully gives you some ideas how to design your own turtle automaton.