How to get keyboard input in pygame?

Question

I am making a game in pygame 1.9.2. It's a faily simple game in which a ship moves between five columns of bad guys who attack by moving slowly downward. I am attempting to make it so that the ship moves left and right with the left and right arrow keys. Here is my code:

keys=pygame.key.get_pressed()
if keys[K_LEFT]:
    location-=1
    if location==-1:
        location=0
if keys[K_RIGHT]:
    location+=1
    if location==5:
        location=4

It works too well. The ship moves too fast. It is near impossible to have it move only one location, left or right. How can i make it so the ship only moves once every time the key is pressed?

Solution 1

You can get the events from pygame and then watch out for the KEYDOWN event, instead of looking at the keys returned by get_pressed()(which gives you keys that are currently pressed down, whereas the KEYDOWN event shows you which keys were pressed down on that frame).

What's happening with your code right now is that if your game is rendering at 30fps, and you hold down the left arrow key for half a second, you're updating the location 15 times.

events = pygame.event.get()
for event in events:
    if event.type == pygame.KEYDOWN:
        if event.key == pygame.K_LEFT:
            location -= 1
        if event.key == pygame.K_RIGHT:
            location += 1

To support continuous movement while a key is being held down, you would have to establish some sort of limitation, either based on a forced maximum frame rate of the game loop or by a counter which only allows you to move every so many ticks of the loop.

move_ticker = 0
keys=pygame.key.get_pressed()
if keys[K_LEFT]:
    if move_ticker == 0:
        move_ticker = 10
        location -= 1
        if location == -1:
            location = 0
if keys[K_RIGHT]:
    if move_ticker == 0:   
        move_ticker = 10     
        location+=1
        if location == 5:
            location = 4

Then somewhere during the game loop you would do something like this:

if move_ticker > 0:
    move_ticker -= 1

This would only let you move once every 10 frames (so if you move, the ticker gets set to 10, and after 10 frames it will allow you to move again)

Solution 2

pygame.key.get_pressed() returns a list with the state of each key. If a key is held down, the state for the key is True, otherwise False. Use pygame.key.get_pressed() to evaluate the current state of a button and get continuous movement:

while True:

    keys = pygame.key.get_pressed()
    x += (keys[pygame.K_RIGHT] - keys[pygame.K_LEFT]) * speed
    y += (keys[pygame.K_DOWN] - keys[pygame.K_UP]) * speed

The keyboard events (see pygame.event module) occur only once when the state of a key changes. The KEYDOWN event occurs once every time a key is pressed. KEYUP occurs once every time a key is released. Use the keyboard events for a single action or movement:

while True:

    for event in pygame.event.get():
        if event.type == pygame.KEYDOWN:
            if event.key == pygame.K_LEFT:
                x -= speed
            if event.key == pygame.K_RIGHT:
                x += speed
            if event.key == pygame.K_UP:
                y -= speed
            if event.key == pygame.K_DOWN:
                y += speed

See also Key and Keyboard event

---

Minimal example of continuous movement: replit.com/@Rabbid76/PyGame-ContinuousMovement

import pygame

pygame.init()
window = pygame.display.set_mode((300, 300))
clock = pygame.time.Clock()

rect = pygame.Rect(0, 0, 20, 20)
rect.center = window.get_rect().center
vel = 5

run = True
while run:
    clock.tick(60)
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            run = False
        if event.type == pygame.KEYDOWN:
            print(pygame.key.name(event.key))

    keys = pygame.key.get_pressed()
    
    rect.x += (keys[pygame.K_RIGHT] - keys[pygame.K_LEFT]) * vel
    rect.y += (keys[pygame.K_DOWN] - keys[pygame.K_UP]) * vel
        
    rect.centerx = rect.centerx % window.get_width()
    rect.centery = rect.centery % window.get_height()

    window.fill(0)
    pygame.draw.rect(window, (255, 0, 0), rect)
    pygame.display.flip()

pygame.quit()
exit()

---

Minimal example for a single action: replit.com/@Rabbid76/PyGame-ShootBullet

import pygame
pygame.init()

window = pygame.display.set_mode((500, 200))
clock = pygame.time.Clock()

tank_surf = pygame.Surface((60, 40), pygame.SRCALPHA)
pygame.draw.rect(tank_surf, (0, 96, 0), (0, 00, 50, 40))
pygame.draw.rect(tank_surf, (0, 128, 0), (10, 10, 30, 20))
pygame.draw.rect(tank_surf, (32, 32, 96), (20, 16, 40, 8))
tank_rect = tank_surf.get_rect(midleft = (20, window.get_height() // 2))

bullet_surf = pygame.Surface((10, 10), pygame.SRCALPHA)
pygame.draw.circle(bullet_surf, (64, 64, 62), bullet_surf.get_rect().center, bullet_surf.get_width() // 2)
bullet_list = []

run = True
while run:
    clock.tick(60)
    current_time = pygame.time.get_ticks()
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            run = False

        if event.type == pygame.KEYDOWN:
            bullet_list.insert(0, tank_rect.midright)

    for i, bullet_pos in enumerate(bullet_list):
        bullet_list[i] = bullet_pos[0] + 5, bullet_pos[1]
        if bullet_surf.get_rect(center = bullet_pos).left > window.get_width():
            del bullet_list[i:]
            break

    window.fill((224, 192, 160))
    window.blit(tank_surf, tank_rect)
    for bullet_pos in bullet_list:
        window.blit(bullet_surf, bullet_surf.get_rect(center = bullet_pos))
    pygame.display.flip()

pygame.quit()
exit()

Solution 3

import pygame
pygame.init()
pygame.display.set_mode()
while True:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            pygame.quit(); #sys.exit() if sys is imported
        if event.type == pygame.KEYDOWN:
            if event.key == pygame.K_0:
                print("Hey, you pressed the key, '0'!")
            if event.key == pygame.K_1:
                print("Doing whatever")

In note that K_0 and K_1 aren't the only keys, to see all of them, see pygame documentation, otherwise, hit tab after typing in

pygame.

(note the . after pygame) into an idle program. Note that the K must be capital. Also note that if you don't give pygame a display size (pass no args), then it will auto-use the size of the computer screen/monitor. Happy coding!

Solution 4

I think you can use:

pygame.time.delay(delayTime)

in which delayTime is in milliseconds.

Put it before events.

Solution 5

The reason behind this is that the pygame window operates at 60 fps (frames per second) and when you press the key for just like 1 sec it updates 60 frames as per the loop of the event block.

clock = pygame.time.Clock()
flag = true
while flag :
    clock.tick(60)

Note that if you have animation in your project then the number of images will define the number of values in tick(). Let's say you have a character and it requires 20 sets images for walking and jumping then you have to make tick(20) to move the character the right way.

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