This is a pygame snake game (Python) I want to draw the snake when it eats but the for loop used is not working

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import pygame
import random
pygame.init()
pygame.font.init()
x = 200
y = 200
wide = 12
height = 12
win = pygame.display.set_mode((900, 500))
f_x = round(random.randrange(900 // 10)*10)
f_y = round(random.randrange(500 // 10)*10)
score = 0
run = True
vel = 1
length = 1


def move():
    global x, y, vel
    key = pygame.key.get_pressed()
    if key[pygame.K_d]:
        x += vel
    if key[pygame.K_a]:
        x -= vel
    if key[pygame.K_w]:
        y -= vel
    if key[pygame.K_s]:
        y += vel


def fon():
    font = pygame.font.Font('freesansbold.ttf', 20)
    txt = font.render("score :" + str(score), True, (0, 255, 0))
    rect = txt.get_rect()
    win.blit(txt, rect)


def draw():
    global f_x, f_y, score, x, y, vel, length
    win.fill((0, 0, 0))
    char = pygame.draw.rect(win, (255, 255, 255), [x, y, wide, height])
    food = pygame.draw.rect(win, (0, 255, 0), (f_x, f_y, wide, height))
    collide = pygame.Rect.colliderect(food, char)
    if collide:
        f_x = round(random.randrange(900 // 10) * 10)
        f_y = round(random.randrange(500 // 10) * 10)
        score += 1
        length += 1



def main():
    global x, y, run, length
    snake_size = []
    while run:
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                pygame.quit()
                quit()
                run = False
        snake_head = []
        snake_head.append(x)
        snake_head.append(y)
        snake_size.append(snake_head)
        print(snake_size)
        print(length)
        if len(snake_size) > length:
            del snake_size[0]
        for x1 in snake_size[:-1]:
            if x1 == snake_head:
                run = True
        for x2 in snake_size:
            pygame.draw.rect(win, (255, 255, 255), (x2[0], x2[1], wide, height))
             # this for loop should draw the snake but it dosent draw it
            


        if x >= 900:
            x = 0
        if x < 0:
            x = 900
        if y >= 500:
            y = 0
        if y < 0:
            y = 500
        draw()
        move()
        fon()
        pygame.display.update()


main()

What I have tried:

i tried a for loop

        for x2 in snake_size:
            pygame.draw.rect(win, (255, 255, 255), (x2[0], x2[1], wide, height))
but it dosent work 
     snake_head = []
        snake_head.append(x)
        snake_head.append(y)
        snake_size.append(snake_head)

Posted 14-Nov-21 4:29am

Athul Manoj

Updated 14-Nov-21 5:04am

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Richard MacCutchan 14-Nov-21 10:55am

"but it dosent work"
And I am afraid that doesn't tell us anything useful. Please use the Improve question link above, and add complete details of what is not working.

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OriginalGriff · Answer 1 · 2021-11-14T05:04:00

Getting your code to run does not mean it is right! :laugh:
Think of the development process as writing an email: compiling successfully means that you wrote the email in the right language - English, rather than German for example - not that the email contained the message you wanted to send.

So now you enter the second stage of development (in reality it's the fourth or fifth, but you'll come to the earlier stages later): Testing and Debugging.

Start by looking at what it does do, and how that differs from what you wanted. This is important, because it give you information as to why it's doing it. For example, if a program is intended to let the user enter a number and it doubles it and prints the answer, then if the input / output was like this:

Input   Expected output    Actual output
  1            2                 1
  2            4                 4
  3            6                 9
  4            8                16

Then it's fairly obvious that the problem is with the bit which doubles it - it's not adding itself to itself, or multiplying it by 2, it's multiplying it by itself and returning the square of the input.
So with that, you can look at the code and it's obvious that it's somewhere here:

C#

int Double(int value)
   {
   return value * value;
   }

Once you have an idea what might be going wrong, start using the debugger to find out why. Put a breakpoint on the first line of the method, and run your app. When it reaches the breakpoint, the debugger will stop, and hand control over to you. You can now run your code line-by-line (called "single stepping") and look at (or even change) variable contents as necessary (heck, you can even change the code and try again if you need to).
Think about what each line in the code should do before you execute it, and compare that to what it actually did when you use the "Step over" button to execute each line in turn. Did it do what you expect? If so, move on to the next line.
If not, why not? How does it differ?
Hopefully, that should help you locate which part of that code has a problem, and what the problem is.
If you don't know how to use the debugger, start here: pdb — The Python Debugger — Python 3.10.0 documentation[^]

This is a skill, and it's one which is well worth developing as it helps you in the real world as well as in development. And like all skills, it only improves by use!