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help with snake game - Printable Version

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help with snake game - blacklight - Jul-24-2020

question: I have a check if the snake.left(x coordinate) == fruit.left, the rand function should be called and the fruit spawns at a different location. It works for the first time their x coordinates are the same, but afterwords it doesn't work anymore. Can anyone help me with this problem?

import pygame
import time
import random

# global variables
game = True
width, height = 500, 500
x, y = 20, 20
x2, y2 = 240, 250

# setting up screen
WIN = pygame.display.set_mode((500,500))
pygame.display.set_caption("Snake by Sam")

# load the background
BG = pygame.image.load("snake.png")
BG_resize = pygame.transform.scale(BG, (width, height))
WIN.blit(BG_resize,(0,0))


# draw square on screen
snake = pygame.draw.rect(WIN, (255,0,0), (x,y,20,20))
key = None

# draw fruit(circle), setup
fruit = pygame.draw.rect(WIN, (255,0,0), (x2,y2,20,20))

def rand():
    global x2, y2
    x2 = random.randint(0, 490)
    y2 = random.randint(0, 490)

def move():
    global key
    global snake
    global x
    global y
    global fruit
    if key == "d":        
        x = snake.left
        time.sleep(0.03)
        x = x + 10
        WIN.blit(BG_resize,(0,0))
        snake = pygame.draw.rect(WIN, (255,0,0), (x,y,20,20))
        fruit = pygame.draw.rect(WIN, (255,0,0), (x2,y2,20,20))

    if key == "s":        
        y = snake.top
        time.sleep(0.03)
        y = y + 10
        WIN.blit(BG_resize,(0,0))
        snake = pygame.draw.rect(WIN, (255,0,0), (x,y,20,20))
        fruit = pygame.draw.rect(WIN, (255,0,0), (x2,y2,20,20))
    if key == "w":        
        y = snake.top
        time.sleep(0.03)
        y = y - 10
        WIN.blit(BG_resize,(0,0))
        snake = pygame.draw.rect(WIN, (255,0,0), (x,y,20,20))
        fruit = pygame.draw.rect(WIN, (255,0,0), (x2,y2,20,20))

    if key == "a":        
        x = snake.left
        time.sleep(0.03)
        x = x - 10
        WIN.blit(BG_resize,(0,0))
        snake = pygame.draw.rect(WIN, (255,0,0), (x,y,20,20))
        fruit = pygame.draw.rect(WIN, (255,0,0), (x2,y2,20,20))

# mainloop
while game:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            game = False
        if event.type == pygame.KEYDOWN:
            if event.key == pygame.K_d:
                WIN.blit(BG_resize,(0,0))
                key = "d"
            if event.key == pygame.K_w:
                WIN.blit(BG_resize,(0,0))
                key = "w"
            if event.key == pygame.K_s:
                WIN.blit(BG_resize,(0,0))
                key = "s"
            if event.key == pygame.K_a:
                WIN.blit(BG_resize,(0,0))
                key = "a"
    move()

    # border control
    if snake.left > 490:
        snake = pygame.draw.rect(WIN, (255,0,0), (250,250,20,20))
        x,y = 250, 250
        key = None
    if snake.left == 0:
        WIN.blit(BG_resize,(0,0))
        snake = pygame.draw.rect(WIN, (255,0,0), (250,250,20,20))
        x,y = 250, 250
        key = None
    if snake.top > 490:
        snake = pygame.draw.rect(WIN, (255,0,0), (250,250,20,20))
        x,y = 250, 250
        key = None
    if snake.top == 0:
        WIN.blit(BG_resize,(0,0))
        snake = pygame.draw.rect(WIN, (255,0,0), (250,250,20,20))
        x,y = 250, 250
        key = None

    # check if the snake has made contact with the fruit.   
    if snake.left == fruit.left: 
        WIN.blit(BG_resize,(0,0))
        rand()
        fruit = pygame.draw.rect(WIN, (255,0,0), (x2,y2,20,20))


    pygame.display.update()


RE: help with snake game - nilamo - Jul-25-2020

When in doubt, print it out!
I added this to your loop: print(f"{snake.left} == {fruit.left}: {snake.left == fruit.left}"), and saw the issue almost immediately.

Your rand() function sets x2 to a random int. In my case, 159. But the snake moves in multiples of 10. So it'll never be at 159. 150 or 160, sure, but never 159.

RE: help with snake game - blacklight - Jul-26-2020

Hi, thanks for your help. After reading your explanation it was clear as day. Didn't realize that because I set the change of the snake to 10 it could never be like 249 or something like that. I also put your print function in my loop and I think it only prints out the x coordinate if x coordinates of both objects are the same. I don't however understand, how you put a conditional in the print statement like that. Could you please explain that to me. It would be much appreciated.

RE: help with snake game - nilamo - Jul-30-2020

That's an "f" string, which means anything inside the curly braces is just python code. You can do whatever you want inside the braces, and whatever it returns (in that case, True/False) will be added to the string. It's not a great idea to do complicated stuff in there, but I didn't really want to write more than one line.