Pygame: key.get_pressed() does not coincide with the event queue

Question

I\'m attempting to work out simple controls for an application using pygame in Python. I have got the basics working, but I\'m hitting a weird wall: I am using the arrow key

Answer 1

For things like movement, you should not check for events (like KEYDOWN or KEYUP), but check every iteration of your mainloop if your movement keys are pressed (using get_pressed).

In your code, you check the pressed keys only if there's also a KEYDOWN event.

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There are also some other things to consider:

• You should seperate the key-mapping and the speed of your player, so it will be easier later on to change either of this.

• You should determine a movement vector and normalize it first, since otherwise, if your vertical and horizontal movement speed is 10, your diagonal movement speed would be ~14.

Working example:

import pygame

pygame.init()

screen = pygame.display.set_mode((200, 200))
run = True
pos = pygame.Vector2(100, 100)
clock = pygame.time.Clock()

# speed of your player
speed = 2

# key bindings
move_map = {pygame.K_LEFT: pygame.Vector2(-1, 0),
            pygame.K_RIGHT: pygame.Vector2(1, 0),
            pygame.K_UP: pygame.Vector2(0, -1),
            pygame.K_DOWN: pygame.Vector2(0, 1)}

while run:
  for e in pygame.event.get():
    if e.type == pygame.QUIT: run = False

  screen.fill((30, 30, 30))
  # draw player, but convert position to integers first
  pygame.draw.circle(screen, pygame.Color('dodgerblue'), [int(x) for x in pos], 10)
  pygame.display.flip()

  # determine movement vector
  pressed = pygame.key.get_pressed()
  move_vector = pygame.Vector2(0, 0)
  for m in (move_map[key] for key in move_map if pressed[key]):
    move_vector += m

  # normalize movement vector if necessary
  if move_vector.length() > 0:
    move_vector.normalize_ip()

  # apply speed to movement vector
  move_vector *= speed

  # update position of player
  pos += move_vector

  clock.tick(60)