Pressing a button to have constant movement

Question

I followed an online tutorial to make a snake game and want some help to make some changes. As of now, holding the left or right arrow keys will cause the snake

Answer 1

The solution is to start off by storing the x,y coordinates of the sprite, set a modifier (increase or decrease amount) on keypress, and then add the modifier to the coordinates while looping. I've written a quick demo of such a system:

import pygame
from pygame.locals import *

pygame.init()
# Set up the screen
screen = pygame.display.set_mode((500,500), 0, 32)
# Make a simple white square sprite
player = pygame.Surface([20,20])
player.fill((255,255,255))

# Sprite coordinates start at the centre
x = y = 250
# Set movement factors to 0
movement_x = movement_y = 0

while True:
    screen.fill((0,0,0))
    for event in pygame.event.get():
        if event.type == KEYDOWN:
            if event.key == K_LEFT:
                movement_x = -0.05
                movement_y = 0
            elif event.key == K_RIGHT:
                movement_x = 0.05
                movement_y = 0
            elif event.key == K_UP:
                movement_y = -0.05
                movement_x = 0
            elif event.key == K_DOWN:
                movement_y = 0.05
                movement_x = 0

    # Modify the x and y coordinates
    x += movement_x
    y += movement_y

    screen.blit(player, (x, y))
    pygame.display.update()

Note that you need to reset the x movement modifier to 0 when changing y, and vice-versa - otherwise you end up with interesting diagonal movements!

For a snake game, you might want to modify the snake size as well as/instead of position - but you should be able to achieve something similar using the same structure.