snake.py

from turtle import Turtle
import random

STARTING_POSITIONS = [(0, 0), (-20, 0), (-40, 0)]
MOVE_DIS = 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 position in STARTING_POSITIONS:
            self.add_seg(position)

    def add_seg(self, position):
        seg = Turtle("circle")
        seg.penup()
        seg.goto(position)
        self.change_color(seg)
        self.segments.append(seg)

    def extend(self):
        # add one seg to snake.
        self.add_seg(self.segments[-1].position())

    def move(self):
        for seg_num in range(len(self.segments)-1, 0, -1):
            new_x = self.segments[seg_num - 1].xcor()
            new_y = self.segments[seg_num - 1].ycor()
            self.segments[seg_num].goto(new_x, new_y)
        self.head.forward(MOVE_DIS)

    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 right(self):
        if self.head.heading() != LEFT:
            self.head.setheading(RIGHT)

    def left(self):
        if self.head.heading() != RIGHT:
            self.head.setheading(LEFT)

    def change_color(self, seg):
        R = random.random()
        B = random.random()
        G = random.random()

        seg.color(R, G, B)