Can constant key input move a sprite constantly?

Question

If I want to move a sprite based on key input in pygame, is there anyway to write code so if I hold down a key, the sprite will keep moving in that direction until I release the key? I've tried this and either the program crashes or I have to repeatedly tap the keys to move the sprite in the intended direction.

Answer 1

The OP wants keystate polling, not KEYDOWN events.

This example shows using both key events, and key polling. You use one for 'on key press' and the other for 'while held down'.

import pygame
from pygame.locals import *

done = False    
player.pos = Rect(0,0,10,10)

while not done:
    for event in pygame.event.get():
        # any other key event input
        if event.type == QUIT:
            done = True        
        elif event.type == KEYDOWN:
            if event.key == K_ESC:
                done = True

    # get key current state
    keys = pygame.key.get_pressed()
    if keys[K_LEFT]:
        player.pos.left -= 10
    if keys[K_RIGHT]:
        player.pos.left += 10
    if keys[K_UP]:
        player.pos.top -= 10
    if keys[K_DOWN]:
        player.pos.left += 10
    if keys[K_SPACE]: 
        print 'firing gun'

Answer 2

As an overview,

• Listen for the KEYDOWN event in the pygame message queue.
• Check if the key you're interested in is pushed down.
• Move in that direction
• Check message queue for KEYUP event that matches your key.
• Stop moving.

Read the documentation as to how to implement this.

Answer 3

You normally use have a moving function in your update method that looks like this:

this.pos_x = direction * speed * delta

Now on your KEYDOWN events you set your direction to 1 or -1 and on KEYUP you set it back to 0. That way you have a nice constant movement.