snake_mech.py

from turtle import Turtle
STARTING_POSITIONS=[(0,0),(-20,0),(-40,0)]
MOVE_DISTANCE=20
UP=90
DOWN=270
LEFT=180
RIGHT=0


class Snake:
    def __init__(self):
        self.segments = []
        self.create_snake()
        self.head = self.segments[0]

    def create_snake(self):
        for postion in STARTING_POSITIONS:
            self.add_segment(position)
    def add_segment(self,position):
            new_segment=Turtle("square")
            new_segment.color("white")
            new_segment.penup()
            new_segment.goto(position)
            self.segments.append(new_segment)
    def extend(self):
        self.add_segment(self.segments[-1].position())


    def move(self):
        for i in range(len(self.segments) - 1, 0, -1):
            x = self.segments[i - 1].xcor()
            y = self.segments[i - 1].ycor()
            self.segments[i].goto(x, y)
        self.head.forward(MOVE_DISTANCE)
    def up(self):
        if self.head.heading()!=DOWN:
            self.head.setheading(UP)
    def down(self):
        if self.head.heading()!=UP:
            self.head.setheading(DOWN)
    def left(self):
        if self.head.heading()!=RIGHT:
            self.head.setheading(LEFT)
    def right(self):
         if self.head.heading()!=LEFT:
            self.head.setheading(RIGHT)