How to move Sprite in Pygame

Question

im trying to get my image (bird) to move up and down on the screen but i cant figure out how to do it here is what i tried im sure its way off but im trying to figure it out if anyone can help that would be great!

import pygame
import os

screen = pygame.display.set_mode((640, 400))

running = 1

while running:
    event = pygame.event.poll()
    if event.type == pygame.QUIT:
        running = 0
    screen.fill([255, 255, 255])
    clock = pygame.time.Clock()
    clock.tick(0.5)
    pygame.display.flip()

    bird = pygame.image.load(os.path.join('C:\Python27', 'player.png'))
    screen.blit( bird, ( 0, 0 ) )

    pygame.display.update()

class game(object):
    def move(self, x, y):
        self.player.center[0] += x
        self.player.center[1] += y


    if event.key == K_UP:
        player.move(0,5)
    if event.key == K_DOWN:
        player.move(0,-5)

game()

im trying to get it to move down on the down button press and up on the UP key press

Answer 1

As stated by ecline6, bird is the least of your worries at this point.

Consider reading this book..

For now, First let's clean up your code...

import pygame
import os

# let's address the class a little later..

pygame.init()
screen = pygame.display.set_mode((640, 400))
# you only need to call the following once,so pull them out of the  while loop.
bird = pygame.image.load(os.path.join('C:\Python27', 'player.png'))
clock = pygame.time.Clock()

running = True
while running:
    event = pygame.event.poll()
    if event.type == pygame.QUIT:
        running = False

    screen.fill((255, 255, 255)) # fill the screen
    screen.blit(bird, (0, 0))    # then blit the bird

    pygame.display.update() # Just do one thing, update/flip.

    clock.tick(40) # This call will regulate your FPS (to be 40 or less)

Now the reason that your "bird" is not moving is:
When you blit the image, ie: screen.blit(bird, (0, 0)),
The (0,0) is constant, so it won't move.

Here's the final code, with the output you want (try it) and read the comments:

import pygame
import os

# it is better to have an extra variable, than an extremely long line.
img_path = os.path.join('C:\Python27', 'player.png')

class Bird(object):  # represents the bird, not the game
    def __init__(self):
        """ The constructor of the class """
        self.image = pygame.image.load(img_path)
        # the bird's position
        self.x = 0
        self.y = 0

    def handle_keys(self):
        """ Handles Keys """
        key = pygame.key.get_pressed()
        dist = 1 # distance moved in 1 frame, try changing it to 5
        if key[pygame.K_DOWN]: # down key
            self.y += dist # move down
        elif key[pygame.K_UP]: # up key
            self.y -= dist # move up
        if key[pygame.K_RIGHT]: # right key
            self.x += dist # move right
        elif key[pygame.K_LEFT]: # left key
            self.x -= dist # move left

    def draw(self, surface):
        """ Draw on surface """
        # blit yourself at your current position
        surface.blit(self.image, (self.x, self.y))


pygame.init()
screen = pygame.display.set_mode((640, 400))

bird = Bird() # create an instance
clock = pygame.time.Clock()

running = True
while running:
    # handle every event since the last frame.
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            pygame.quit() # quit the screen
            running = False

    bird.handle_keys() # handle the keys

    screen.fill((255,255,255)) # fill the screen with white
    bird.draw(screen) # draw the bird to the screen
    pygame.display.update() # update the screen

    clock.tick(40)

Answer 2

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 a step-by-step movement.

If you want to achieve a continuously movement, you have to use pygame.key.get_pressed(). 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.

See also Key and Keyboard event and How can I make a sprite move when key is held down.

---

Minimal example:

import pygame
import os

class Bird(object):
    def __init__(self):
        self.image = pygame.image.load(os.path.join('C:\Python27', 'player.png'))
        self.center = [100, 200]

    def move(self, x, y):
        self.center[0] += x
        self.center[1] += y

    def draw(self, surf):
        surf.blit(self.image, self.center)

class game(object):
    
    def __init__(self):
        self.screen = pygame.display.set_mode((640, 400))
        self.clock = pygame.time.Clock()
        self.player = Bird()

    def run(self):
        running = 1
        while running:
            self.clock.tick(60)
            event = pygame.event.poll()
            if event.type == pygame.QUIT:
                running = 0
            
            keys = pygame.key.get_pressed()
            move_x = keys[pygame.K_RIGHT] - keys[pygame.K_LEFT]
            move_y = keys[pygame.K_DOWN] - keys[pygame.K_UP]
            self.player.move(move_x * 5, move_y * 5)

            self.screen.fill([255, 255, 255])
            self.player.draw(self.screen)
            pygame.display.update()

g = game()
g.run()