Python Snake Game snake does not follow

Question

I am creating Snake game in pygame using Sprite logic

how do i chain the movement of the snake? another question on this has been answered here but i cant apply it to my code: see here

the minimal example above works. try it first and you will see my issue :) the snake grows on collision with the red food... but its movement does not chain

thank you

import pygame
from random import randint
from sys import exit

pygame.init()
game_active = True #start the game on the Welcome Screen
clock = pygame.time.Clock() #an object to track time, for fps


def display_surface():
    """function to create the main window"""
    disp_surface = pygame.display.set_mode(size = (610, 700)) #creates a main display window
    pygame.display.set_caption("Snake")
    return disp_surface
disp_surface = display_surface() #MUST return this immediately so it can be pushed to pygame.display.update()

class snake(pygame.sprite.Sprite):
    def __init__(self, x_pos = 300, y_pos = 300):
        #Access the super class of Sprite
        super().__init__()
        image1 = pygame.image.load("square1.png").convert_alpha()
        self.x_pos = x_pos
        self.y_pos = y_pos

        self.image = image1
        self.rect = self.image.get_rect(x = x_pos, y = y_pos)

    def update(self, left, right, up, down):
        """defines the movement of the snake using arrow keys"""
        if left:
            self.rect.left -= 1
        if right:
            self.rect.right += 1
        if up:
            self.rect.top -= 1
        if down:
            self.rect.bottom += 1

snakegroup = pygame.sprite.Group()
original_snake = snake()
snakegroup.add(original_snake)

class food(pygame.sprite.Sprite):
    """class to control food action"""
    def __init__(self):
        super().__init__() #access the Sprite super class methods
        food1 = pygame.image.load("food1.png").convert_alpha()
        x_pos = randint(50,600)
        y_pos = randint(50,650)
        self.image = food1
        self.rect = self.image.get_rect(x = x_pos,y = y_pos)

foods = pygame.sprite.GroupSingle()
foods.add(food())

multiplier_x_pos = 1
while True:
    """EVENT LOOP CODE"""
    for eachevent in pygame.event.get():
        if eachevent.type == pygame.QUIT:
            pygame.quit()
            exit()

        game_active = True
        if pygame.sprite.spritecollideany(foods.sprite, snakegroup):
            foods.empty()
            foods.add(food())
            foods.draw(disp_surface)

            snakegroup.add(snake(original_snake.rect.x-(25*multiplier_x_pos),original_snake.rect.y))
            multiplier_x_pos += 1
            snakegroup.update(left, right, up, down)
            
        
        keys = pygame.key.get_pressed()
        events = pygame.event.get()
        
        left = keys[pygame.K_LEFT]
        right = keys[pygame.K_RIGHT]
        up = keys[pygame.K_UP]
        down = keys[pygame.K_DOWN]
     
        snakegroup.update(left,right,up,down)

    """PYGAME EVENT CODE"""
    if game_active:
        disp_surface = display_surface()

        snakegroup.draw(disp_surface)
        foods.draw(disp_surface)

    else:
        disp_surface.fill((64,64,64))

    pygame.display.update() #update all the surfaces on each frame
    clock.tick(120) #fps

i think you should follow a tutorial because implementing that is tricky, basically you'll need 2 different parts in snake lets say one is head and all other are tail objects, so head can move in 3 directions and tail just follows it one by one. — Pratik Agrawal, Feb 09 '22 at 18:10
Thing is I've built this 80% based on my learnings about pygame and sprites. I never googled how to make snake in python until today. I want to finish this code as opposed to totally rewriting my game based on what a snake tutorial says as that will change most of my code — mojo3340, Feb 09 '22 at 18:17

score 2 · Accepted Answer · answered Feb 09 '22 at 18:44

See the answer referenced in your question How do I chain the movement of a snake's body?.

You need to use the 2nd solution and adjust the function that creates the snake body. The new function needs to update the positions of the Snakes body Sprites:

def update_body(track, distance):
    body = snakegroup.sprites()
    no_parts = len(body)
    body[0].update(*track[0])
    track_i = 1
    next_i = 1
    for i in range(1, no_parts):
        while track_i < len(track):
            pos = track[track_i]
            track_i += 1
            dx, dy = body[i-1].x_pos-pos[0], body[i-1].y_pos-pos[1]
            if math.sqrt(dx*dx + dy*dy) >= distance:
                body[i].update(*pos)
                next_i = i+1
                break
    while next_i < no_parts:
        body[next_i].update(*track[-1])
        next_i += 1
    del track[track_i:]
    return body

Example based on your (revised) code:

import pygame
import math
from random import randint
from sys import exit

pygame.init()
clock = pygame.time.Clock()
disp_surface = pygame.display.set_mode(size = (610, 700))

class Snake(pygame.sprite.Sprite):
    def __init__(self, x_pos = 300, y_pos = 300):
        #Access the super class of Sprite
        super().__init__()
        #self.image = pygame.image.load("square1.png").convert_alpha()
        self.image = pygame.Surface((20, 20), pygame.SRCALPHA)
        pygame.draw.circle(self.image, (0, 255, 0), (10, 10), 10)
        self.x_pos = x_pos
        self.y_pos = y_pos
        self.rect = self.image.get_rect(x = x_pos, y = y_pos)
    def update(self, x_pos, y_pos):
        self.x_pos = x_pos
        self.y_pos = y_pos
        self.rect = self.image.get_rect(center = (x_pos, y_pos))

class Food(pygame.sprite.Sprite):
    """class to control food action"""
    def __init__(self):
        super().__init__() #access the Sprite super class methods
        #self.image = pygame.image.load("food1.png").convert_alpha()
        self.image = pygame.Surface((20, 20), pygame.SRCALPHA)
        pygame.draw.circle(self.image, (255, 0, 0), (10, 10), 10)
        x_pos = randint(50,600)
        y_pos = randint(50,650)
        self.rect = self.image.get_rect(x = x_pos,y = y_pos)
    def update(self, pos):
        x_pos = randint(50,600)
        y_pos = randint(50,650)
        self.rect = self.image.get_rect(x = x_pos,y = y_pos)


def update_body(track, distance):
    body = snakegroup.sprites()
    no_parts = len(body)
    body[0].update(*track[0])
    track_i = 1
    next_i = 1
    for i in range(1, no_parts):
        while track_i < len(track):
            pos = track[track_i]
            track_i += 1
            dx, dy = body[i-1].x_pos-pos[0], body[i-1].y_pos-pos[1]
            if math.sqrt(dx*dx + dy*dy) >= distance:
                body[i].update(*pos)
                next_i = i+1
                break
    while next_i < no_parts:
        body[next_i].update(*track[-1])
        next_i += 1
    del track[track_i:]
    return body

snakegroup = pygame.sprite.Group()
original_snake = Snake()
snakegroup.add(original_snake)
track = [(original_snake.x_pos, original_snake.y_pos)]

foods = pygame.sprite.GroupSingle()
foods.add(Food())

direction = (0, 0)
speed = 1
run = True
while run:
    for eachevent in pygame.event.get():
        if eachevent.type == pygame.QUIT:
            run = False
        if eachevent.type == pygame.KEYDOWN:
            if eachevent.key == pygame.K_LEFT and direction[0] != 1:
                direction = (-1, 0)
            if eachevent.key == pygame.K_RIGHT and direction[0] != -1:
                direction = (1, 0)
            if eachevent.key == pygame.K_UP and direction[1] != 1:
                direction = (0, -1)
            if eachevent.key == pygame.K_DOWN and direction[1] != -1:
                direction = (0, 1)

    track.insert(0, track[0][:])    
    track[0] = (track[0][0] + direction[0] * speed) % disp_surface.get_width(), (track[0][1] + direction[1] * speed) % disp_surface.get_height()
    update_body(track, 20)

    if pygame.sprite.spritecollideany(foods.sprite, snakegroup):
        foods.empty()
        foods.add(Food())
        last_part = snakegroup.sprites()[-1]
        snakegroup.add(Snake(last_part.x_pos, last_part.y_pos))
        speed = min(10, speed + 1)
            
    disp_surface.fill((64,64,64))    
    snakegroup.draw(disp_surface)
    foods.draw(disp_surface)
    pygame.display.update()
    clock.tick(120)

Python Snake Game snake does not follow

1 Answers1