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Pygame Delttime Function to go to the Right is 10 times slower than when I go to the left [duplicate]

This question already has answers here:
Pygame doesn't let me use float for rect.move, but I need it
(2 answers)
Closed 1 year ago.
Hello Stackoverflow Community,
could someone help me with my problem.
When I move to the left I am quite fast but when I want to go to the right it takes way to lang. I deleted the dt from my move function and the went the same speed. I changed the buttons but the problem seems only to occure when I use the +=. Does one of you dealt with the problem before and could help me?
import pygame
import time
import random
#0 = Menu, 1 = Game, 2 = Quit
game_state = 1
WHITE = (255, 255, 255)
class Player(pygame.sprite.Sprite):
speed = 100
def __init__(self, WIDTH):
pygame.sprite.Sprite.__init__(self)
self.image = pygame.image.load("player.png")
self.rect = self.image.get_rect()
self.rect.center = (WIDTH / 2, 480)
def move(self, keys, dt):
if(keys[0]):
self.rect.x += self.speed * dt
print(self.speed)
print(dt)
print(self.rect.x)
if(keys[1]):
print(self.speed)
print(dt)
self.rect.x -= self.speed * dt
print(self.rect.x)
class Main():
prev_time = time.time()
dt = 0
#initalizing menu or game depending on variables
def __init__(self):
global game_state
while game_state !=2:
WIDTH, HEIGHT = 800, 600
screen = self.initialize_pygame("Alien Slaughter", WIDTH, HEIGHT)
self.all_sprites = pygame.sprite.Group()
self.player = Player(WIDTH)
self.all_sprites.add(self.player)
if(game_state == 1):
self.prev_time = time.time()
self.game(screen, WIDTH, HEIGHT)
#calculating deltatime
def calc_deltatime(self):
self.now = time.time()
self.dt = self.now - self.prev_time
self.prev_time = self.now
#initializing pygame and create window
def initialize_pygame(self, title, width, height):
screen = pygame.display.set_mode((width, height))
pygame.display.set_caption(title)
icon = pygame.image.load("icon.png")
pygame.display.set_icon(icon)
pygame.init()
return screen
def handle_inputs(self, keys, event):
if event.type == pygame.KEYDOWN:
if event.key == pygame.K_d:
keys[0] = True
if event.key == pygame.K_a:
keys[1] = True
if event.type == pygame.KEYUP:
if event.key == pygame.K_d:
keys[0] = False
if event.key == pygame.K_a:
keys[1] = False
def game(self, screen, width, height):
global game_state
BLACK = (100, 100, 100)
keys = [False, False]
#Game loop
while game_state == 1:
#Process input (events)
for event in pygame.event.get():
#Check for Closing windows
if event.type == pygame.QUIT:
game_state = 2
self.handle_inputs(keys, event)
self.calc_deltatime()
self.player.move(keys, self.dt)
#Update
self.all_sprites.update()
#Draw / render
screen.fill(BLACK)
self.all_sprites.draw(screen)
pygame.display.update()
game = Main()

Since pygame.Rect is supposed to represent an area on the screen, a pygame.Rect object can only store integral data.
The coordinates for Rect objects are all integers. [...]
The fraction part of the coordinates gets lost when the movement is added to the coordinates of the Rect object. If this is done every frame, the position error will accumulate over time.
If you want to store object positions with floating point accuracy, you have to store the location of the object in separate variables respectively attributes and to synchronize the pygame.Rect object. round the coordinate and assign it to the location of the rectangle:
class Player(pygame.sprite.Sprite):
speed = 100
def __init__(self, WIDTH):
pygame.sprite.Sprite.__init__(self)
self.image = pygame.image.load("player.png")
self.rect = self.image.get_rect()
self.rect.center = (WIDTH / 2, 480)
self.x = self.rect.x
def move(self, keys, dt):
if keys[0]:
self.x += self.speed * dt
if keys[1]:
self.x -= self.speed * dt
self.rect.x = round(self.x)

How to make gravity function in pygame?

Unable to move player in pygame
So, I was trying to create a simple physics system in pygame. My main goal was to add a Y gravity function that would move the player when activated. I have tried several times to make it work, but I guess I am missing something.
Here is the code:
class Physic:
def __init__(self, color, master, type, sizeX, sizeY, pos=[0,0]):
self.master = master
self.color = color
self.type = type
self.sizeX = sizeX
self.sizeY = sizeY
self.x = pos[0]
self.y = pos[1]
self.moveX = 0
self.moveY = 0
self.create_Object()
def create_Object(self):
if self.type == 'rect':
self.rect()
def rect(self):
return pygame.draw.rect(self.master, self.color, (self.x, self.y, self.sizeX, self.sizeY))
def drag(self):
for event in pygame.event.get():
if event.type == pygame.mouse.get_pressed()[0]:
self.x = pygame.mouse.get_pos()
def add_gravity(self):
self.moveY += 3.2
self.update_pos()
def update_pos(self):
self.y += self.moveY
self.x += self.moveX
In the main script I put this:
def game():
while True:
for event in pygame.event.get():
if event.type == pygame.QUIT:
sys.exit()
screen.fill(WHITE)
player = object.Physic(BLUE, screen, 'rect', 50, 50, [POS[0], POS[1]])
player.add_gravity()
# platform = object.rect(screen, RED, [30, 30], 100, 30)
# physics.add_collider(player, platform, POS[0])
pygame.display.update()
game()
Do you know what I am missing?

Your big problem is that you are recreating the player every pass inside the main loop and so it looks like it is frozen in place.
You also need to have a limit on the frame rate so that you control the speed of the game and therefor can properly set the acceleration per frame.
There are a some other minor things that needed to be fixed to run this. I tried to change the minimum possible to run it, since the point was to fix the error rather than rewrite it on you. Obviously I had to add some wrapper code around it
Try this slightly adjusted version:
#!/usr/bin/env python
import traceback
import pygame
import sys
FRAME_RATE = 60
GRAVITY = 32
SCREEN_SIZE = (600, 800)
WHITE = pygame.Color("white")
BLUE = pygame.Color("blue")
POS = (100, 600)
class Physic:
def __init__(self, color, master, type, sizeX, sizeY, pos=(0,0)):
self.master = master
self.color = color
self.type = type
self.sizeX = sizeX
self.sizeY = sizeY
self.x = pos[0]
self.y = pos[1]
self.moveX = 0
self.moveY = 0
self.create_Object()
def create_Object(self):
if self.type == 'rect':
self.draw()
def draw(self):
return pygame.draw.rect(self.master, self.color, (self.x, self.y, self.sizeX, self.sizeY))
def drag(self):
for event in pygame.event.get():
#if event.type == pygame.mouse.get_pressed()[0]: <--- remove this
if event.type == pygame.MOUSEBUTTONDOWN:
self.x = pygame.mouse.get_pos()
def add_gravity(self):
self.moveY += GRAVITY / FRAME_RATE
self.update_pos()
def update_pos(self):
self.y += self.moveY
self.x += self.moveX
def game():
pygame.init()
screen = pygame.display.set_mode(SCREEN_SIZE)
clock = pygame.time.Clock()
player = Physic(BLUE, screen, 'rect', 50, 50, POS)
# I added this to illustrate the gravity better ... going up and down
player.moveY = -25
player.moveX = 2
while True:
for event in pygame.event.get():
if event.type == pygame.QUIT:
return
screen.fill(WHITE)
player.add_gravity()
player.draw()
# platform = object.rect(screen, RED, [30, 30], 100, 30)
# physics.add_collider(player, platform, POS[0])
pygame.display.update()
clock.tick(FRAME_RATE)
def main():
try:
game()
except Exception as ex:
print(traceback.format_exc())
raise
finally:
# game exit cleanup stuff
pygame.quit()
if __name__ == '__main__':
main()
An issue that I want to point out though it is not affecting this code here. You should not use an immutable object (like a list) as an default when defining an optional/named argument in a method. I.e. in the Physic __init__() I changed pos=[0,0] to pos=(0,0). Not a big deal here, but can cause really odd bugs if you had assigned it to a var, then tried to change it. It will have effects on other instances of the object because they actually share the default initialization object and if it gets modified by one of them it happens in all of them!

A surface shown unexpectedly with pygame

I'm in the process of making a snake game, it mostly went well so far, but it displayed a block of the snake at the top left that I can't get rid of.
I checked that I didn't draw the surface there(0,0). I'm stuck. Please help me out, thanks!!
BTW it's my first time asking a question so any suggestion on that is also appreciated.
Edit: I found that using a regular class instead of sprite solved the problem, but I need the collide and other functions in sprite.
import pygame
class snake(pygame.sprite.Sprite):
speed=5
init_length=10
direction=0
x=[]
y=[]
updateCountMax = 2
updateCount = 0
length=10
# image=pygame.Surface((11,11)).convert().fill((0,128,255))
def __init__(self,init_x,init_y,image,screen):
pygame.sprite.Sprite.__init__(self)
for i in range(0,self.init_length):
self.x.append(init_x)
self.y.append(init_y)
# for i in range(0,self.length):
# print(f"{self.x[i]},{self.y[i]}")
for x in self.x:
print(x)
for y in self.y:
print(y)
self.image=image
self.screen=screen
self.rect=self.image.get_rect()
# self.rect.center=(self.x,self.y)
def move_R(self):
# self.x+=self.speed
self.direction=0
def move_L(self):
# self.x-=self.speed
self.direction=1
def move_U(self):
# self.y-=self.speed
self.direction=2
def move_D(self):
# self.y+=self.speed
self.direction=3
def update(self):
# self.updateCount = self.updateCount + 1
# if self.updateCount < self.updateCountMax:
for i in range(self.length-1,0,-1):
# print("self.x[" + str(i) + "] = self.x[" + str(i-1) + "]")
self.x[i] = self.x[i-1]
self.y[i] = self.y[i-1]
if(self.direction==0):
self.x[0]+=self.speed
elif(self.direction==1):
self.x[0]-=self.speed
elif(self.direction==2):
self.y[0]-=self.speed
elif(self.direction==3):
self.y[0]+=self.speed
# self.rect.center=(self.x,self.y)
# self.updateCount = 0
# for i in range(0,self.length):
# print(f"{self.x[i]},{self.y[i]}")
self.draw()
def draw(self):
for i in range(0,self.length):
self.screen.blit(self.image,(self.x[i],self.y[i]))
# print(f"rendered at {self.x[i]},{self.y[i]}")
# self.rect.center=(self.x[i],self.y[i])
class app:
width=1200
height=900
title="Snake"
done=False
def __init__(self):
pygame.init()
self.image=pygame.Surface((11,11))
self.image.fill((0,128,255))
pygame.display.set_caption(self.title)
self.screen = pygame.display.set_mode((self.width, self.height))
self.screen.fill((0,0,0))
self.clock=pygame.time.Clock()
self.snakes=pygame.sprite.Group()
self.player1=snake(500,10,self.image,self.screen)
self.snakes.add(self.player1)
self.background = pygame.Surface(self.screen.get_size())
self.background = self.background.convert()
self.background.fill((255,255,255))
def loop(self):
while(not self.done):
for event in pygame.event.get():
if event.type == pygame.QUIT:
self.done = True
pygame.event.pump()
keys = pygame.key.get_pressed()
if (keys[pygame.K_RIGHT]):
self.player1.move_R()
if (keys[pygame.K_LEFT]):
self.player1.move_L()
if (keys[pygame.K_UP]):
self.player1.move_U()
if (keys[pygame.K_DOWN]):
self.player1.move_D()
if (keys[pygame.K_ESCAPE]):
self.done = True
self.screen.blit(self.background,(0,0))
self.screen.fill((0,0,0))
self.player1.update()
self.snakes.draw(self.screen)
pygame.display.update()
self.clock.tick(60)
pygame.quit()
if __name__ == "__main__" :
theApp = app()
theApp.loop()

You add player1 to the snakes sprite group and draw that with self.snakes.draw(self.screen). However, you also draw the player in self.player1.update(), in the last line.
Remove self.snakes.draw(self.screen) to get rid of the phantom snake.
BTW: you create and set a self.background but you immediately overwrite it with self.screen.fill((0,0,0)), so you don't need a background at all.

What you see in the top left corner is the self.image of the player1 sprite. The draw method of sprite groups blits the images at the rect.topleft coordinates of the sprites and since you never move the player1.rect, the image will be blitted at the default (0, 0) coordinates. So just remove the line self.snakes.draw(self.screen) to fix this.
I also suggest that you use pygame.Rects instead of the self.x and self.y lists. You can create rect instances with the init_x and init_y coords as the topleft attribute and put them into a self.rects list. That allows you to simplify the update and draw methods, and the rects can also be used for the collision detection. I've already refactored your code (it kind of became a mini code review):
import pygame
class Snake(pygame.sprite.Sprite): # Use upper camelcase names for classes (see PEP 8).
def __init__(self, init_x, init_y, image,screen):
pygame.sprite.Sprite.__init__(self)
# These are instance attributes now (use class attributes if
# the values should be shared between the instances).
self.speed = 5
self.init_length = 10
self.direction = 0
self.updateCountMax = 2
self.updateCount = 0
self.length = 10
# The body parts are rects now.
self.rects = []
for i in range(self.init_length):
# Append pygame.Rect instances.
self.rects.append(pygame.Rect(init_x, init_y, 11, 11))
self.image = image
self.screen = screen
self.rect = self.rects[0] # I use the first rect as the self.rect.
def update(self):
for i in range(self.length-1, 0, -1):
# Update the topleft (x, y) positions of the rects.
self.rects[i].topleft = self.rects[i-1].topleft
if self.direction == 0:
self.rects[0].x += self.speed
elif self.direction == 1:
self.rects[0].x -= self.speed
elif self.direction == 2:
self.rects[0].y -= self.speed
elif self.direction == 3:
self.rects[0].y += self.speed
def draw(self):
# Iterate over the rects to blit them (I draw the outlines as well).
for rect in self.rects:
self.screen.blit(self.image, rect)
pygame.draw.rect(self.screen, (0, 255, 0), rect, 1)
class App:
width = 1200
height = 900
title = "Snake"
done = False
def __init__(self):
pygame.init()
self.image = pygame.Surface((11, 11))
self.image.fill((0, 128, 255))
pygame.display.set_caption(self.title)
self.screen = pygame.display.set_mode((self.width, self.height))
self.clock = pygame.time.Clock()
self.snakes = pygame.sprite.Group()
self.player1 = Snake(500, 10, self.image, self.screen)
self.snakes.add(self.player1)
def loop(self):
while not self.done:
# Handle the events.
for event in pygame.event.get():
if event.type == pygame.QUIT:
self.done = True
keys = pygame.key.get_pressed()
# In Python we simply set the values of the
# attributes directly instead of using getter
# and setter methods.
if keys[pygame.K_RIGHT]:
self.player1.direction = 0
if keys[pygame.K_LEFT]:
self.player1.direction = 1
if keys[pygame.K_UP]:
self.player1.direction = 2
if keys[pygame.K_DOWN]:
self.player1.direction = 3
if keys[pygame.K_ESCAPE]:
self.done = True
# Update the game.
self.player1.update()
# Draw everything.
self.screen.fill((0, 0, 0))
self.player1.draw()
pygame.draw.rect(self.screen, (255, 0, 0), self.player1.rect, 1)
pygame.display.update()
self.clock.tick(60)
pygame.quit()
if __name__ == "__main__" :
the_app = App()
the_app.loop()

How to change variables inside a class at runtime?

Follow-up question on my previous question.
After I got the circle to show up properly, I wish to be able to move that circle now with keyboard input.
Since it is a class I am trying to change I must have an instance so that I change the same instance of the class all the time, and I do have one.
import pygame
pygame.init()
#Colors
black = (0,0,0)
white = (255,255,255)
red = (255,0,0)
green = (0,255,0)
blue = (0,0,255)
#Display
display_width, display_height = 800, 600
screen_center = int(display_width * 0.5), int(display_height * 0.5)
screen = pygame.display.set_mode((display_width, display_height))
#Clock
clock = pygame.time.Clock()
class Player():
def __init__(self):
self.xPos = int(display_width * 0.5)
self.yPos = int(display_height * 0.5)
self.color = blue
self.radius = 15
self.width = 0
pygame.draw.circle(screen, self.color, (self.xPos, self.yPos), self.radius, self.width)
def game_loop():
player = Player() #PLAYER CLASS INSTANCE
running = True
while running:
for event in pygame.event.get():
if event.type == pygame.QUIT:
pygame.quit()
running = False
if event.type == pygame.KEYDOWN:
if event.key == pygame.K_LEFT:
player.color = blue # THESE COLORS ARE MAINLY HERE FOR DEBUGGING
if event.key == pygame.K_RIGHT:
player.color = red # THESE COLORS ARE MAINLY HERE FOR DEBUGGING
if event.key == pygame.K_UP:
pass
if event.key == pygame.K_DOWN:
pass
#Background
screen.fill(white)
#Draw everything in order, each drawn object will be drawn beneath the next drawn object.
player
#Update
pygame.display.update()
clock.tick(60)
game_loop()
So whenever I press the left key for example, the xPos inside the class must change so that my circle moves.

You could try changing your player class to make it have a separat emethod for drawing itself:
class Player():
def __init__(self):
self.xPos = int(display_width * 0.5)
self.yPos = int(display_height * 0.5)
self.color = blue
self.radius = 15
self.width = 0
def draw(self):
pygame.draw.circle(screen, self.color, (self.xPos, self.yPos), self.radius, self.width)
Then inside your main loop, call player.draw() after you've done the screen fill:
#Background
screen.fill(white)
#Draw everything in order, each drawn object will be drawn beneath the next drawn object.
player.draw()
Now the player object wont draw itself when it's created, instead it will be drawn during every iteration of your main loop.

Multiple bullets not showing up when added to Pygame sprite group and updated

I'm working on my first project in Python / Pygame, which is a shooter-style game. However, when I create multiple instances of my Bullet sprite and add them to the sprite group, only the most recent instance is shown on the screen. That is, only one bullet is showing at any given time.
I think Lines 175-180 or within the Bullet class are causing the problem.
My code:
import pygame, random , sys , time
from pygame.locals import *
# Screen dimensions
SCREEN_WIDTH = 640
SCREEN_HEIGHT = 480
# Global constants
WHITE = (255, 255, 255)
BLACK = ( 0, 0, 0)
LIGHTBLUE = ( 0, 0, 155)
FPS = 60
class Player(pygame.sprite.Sprite):
# set speed vector of the player
change_x = 0
change_y = 0
moverate = 5
# Constructor. Pass in x and y position
def __init__(self, x, y):
# Call the parent class (Sprite) constructor
pygame.sprite.Sprite.__init__(self)
# Create player image
self.image = pygame.image.load('player.png')
self.image.set_colorkey(WHITE)
# Set a referance to the image rect.
self.rect = self.image.get_rect()
self.rect.centerx = x
self.rect.y = y
def changespeed(self, x, y):
""" Change the speed of the player"""
self.change_x += x
self.change_y += y
def update(self):
""" Move the player. """
# Move left/right
self.rect.x += self.change_x
# Move up/down
self.rect.y += self.change_y
def stop(self):
""" Called when the user lets off the keyboard."""
self.change_x = 0
self.change_y = 0
self.image = pygame.image.load('player.png')
self.image.set_colorkey(WHITE)
class Enemy(pygame.sprite.Sprite):
""" This class represents the enemy sprites."""
minmoverate = 1
maxmoverate = 8
def __init__(self):
# Call the parent class (Sprite) constructor
pygame.sprite.Sprite.__init__(self)
self.image = pygame.image.load('enemyShip.png')
self.image = pygame.transform.scale(self.image, (50, 50))
self.image.set_colorkey(WHITE)
self.rect = self.image.get_rect()
def reset_pos(self):
""" Reset position to the top of the screen, at a random x location.
Called by update() or the main program loop if there is a collision."""
self.rect.y = - ( SCREEN_HEIGHT / 4)
self.rect.x = random.randrange(SCREEN_WIDTH)
def update(self):
""" Move the enemies. """
# Move down, at some speed
self.rect.y += 2
# Move left and right, at some speed
self.rect.x += 0
# If enemy is too far down, reset to top of screen
if self.rect.y > SCREEN_HEIGHT:
self.reset_pos()
class Bullet(pygame.sprite.Sprite):
""" This class represents the bullet. """
def __init__(self):
# Call the parent class (Sprite) constructor
pygame.sprite.Sprite.__init__(self)
self.image = pygame.Surface([8, 20])
self.image.fill(LIGHTBLUE)
self.rect = self.image.get_rect()
def update(self):
""" Move the bullet. """
self.rect.y -= 10
class Game(object):
""" This class represents an instance of the game. If we need to
rest the game we'd just need to create a new instance of this class."""
# --- Class attributes.
# Sprite lists
enemy_list = None
bullet_list = None
all_sprites_list = None
# --- Class methods
# Set up the game
def __init__(self):
self.score = 0
self.game_over = False
# Create sprite lists
self.enemy_list = pygame.sprite.Group()
self.bullet_list = pygame.sprite.Group()
self.all_sprites_list = pygame.sprite.Group()
# Create the starting enemy ships
for i in range(15):
enemy = Enemy()
enemy.rect.x = random.randrange(SCREEN_WIDTH)
enemy.rect.y = random.randrange(-300, 20)
self.enemy_list.add(enemy)
self.all_sprites_list.add(enemy)
# Create the player
self.player = Player(SCREEN_WIDTH / 2, SCREEN_HEIGHT - (SCREEN_HEIGHT / 6))
self.all_sprites_list.add(self.player)
def process_events(self):
""" Process all of the events. Return "True" if we need to close the window."""
for event in pygame.event.get():
if event.type == pygame.QUIT:
return True
elif event.type == KEYDOWN:
if event.key == K_ESCAPE:
return True
elif event.key == K_RETURN:
if self.game_over:
self.__init__()
elif event.key in (K_RIGHT ,K_d):
self.player.changespeed( self.moverate ,0)
elif event.key in (K_LEFT ,K_a):
self.player.changespeed( -self.moverate ,0)
elif event.key in (K_UP , K_w):
self.player.changespeed(0, -self.moverate)
elif event.key in (K_DOWN , K_s):
self.player.changespeed(0, self.moverate)
elif event.key == K_SPACE: # Fire bullet
bullet = Bullet(0
# Set bullet so it is where the player is
bullet.rect.centerx = self.player.rect.centerx
bullet.rect.y = self.player.rect.y
# Add bullet to lists
self.all_sprites_list.add(bullet)
self.bullet_list.add(bullet)
elif event.type == KEYUP:
if event.key in (K_RIGHT ,K_d):
self.player.changespeed( -self.moverate ,0)
elif event.key in (K_LEFT ,K_a):
self.player.changespeed( self.moverate ,0)
elif event.key in (K_UP , K_w):
self.player.changespeed(0, self.moverate)
elif event.key in (K_DOWN , K_s):
self.player.changespeed(0, -self.moverate)
def run_logic(self):
""" This method is run each time through the frame.
It updates positions and checks for collisions."""
enemy = Enemy()
if not self.game_over:
# Move all the sprites
self.all_sprites_list.update()
if len(self.all_sprites_list) < 17:
self.enemy_list.add(enemy)
self.all_sprites_list.add(enemy)
enemy.rect.x = random.randrange(SCREEN_WIDTH)
enemy.rect.y = random.randrange(-100, -50)
# Bullet Mechanics
for bullet in self.bullet_list:
# See if the bullets has collided with anything.
self.enemy_hit_list = pygame.sprite.spritecollide(bullet, self.enemy_list, True)
# For each enemy hit, remove bullet and enemy and add to score
for enemy in self.enemy_hit_list:
self.bullet_list.remove(bullet)
self.all_sprites_list.remove(bullet)
self.score += 1
# Remove the bullet if it flies up off the screen
if bullet.rect.y < -10:
self.bullet_list.remove(bullet)
self.all_sprites_list.remove(bullet)
# Player Mechanics
for enemy in self.enemy_list:
# See if player has collided with anything.
self.player_hit_list = pygame.sprite.spritecollide(self.player, self.enemy_list, True)
if len(self.player_hit_list) == 1:
# If player is hit, show game over.
self.game_over = True
def display_frame(self, screen):
""" Display everything to the screen for the game. """
screen.fill(BLACK)
if self.game_over:
# font = pygame.font.Font("Serif:, 25)
font = pygame.font.SysFont("serif", 25)
text = font.render("Game Over! You scored " + str(self.score) +" points, press Enter to restart", True, WHITE)
center_x = (SCREEN_WIDTH // 2) - (text.get_width() // 2)
center_y = (SCREEN_HEIGHT // 2) - (text.get_height() // 2)
screen.blit(text, [center_x, center_y])
if not self.game_over:
self.all_sprites_list.draw(screen)
pygame.display.flip()
def main():
""" Main program function. """
# Initialize Pygame and set up the window
pygame.init()
size = [SCREEN_WIDTH, SCREEN_HEIGHT]
screen = pygame.display.set_mode(size)
screen_rect = screen.get_rect()
pygame.display.set_caption("My Game")
pygame.mouse.set_visible(False)
# Create our objects and set the data
done = False
clock = pygame.time.Clock()
# Create an instance of the Game class
game = Game()
# Main game loop
while not done:
# Process events (keystrokes, mouse clicks, etc)
done = game.process_events()
# Update object positions, check for collisions
game.run_logic()
# Draw the current frame
game.display_frame(screen)
# Pause for the next frame
clock.tick(FPS)
# Close window and exit
pygame.quit()
# Call the main function, start up the game
if __name__ == "__main__":
main()

The problem is that you're only ever creating a single Bullet instance, which you're storing in the Game.bullet class variable. Whenever you shoot, the code moves that single bullet to the player's position, and it updates from there.
You probably want to create a new bullet for every shot. Use something like this in process_events:
elif event.key == K_SPACE: # Fire bullet
bullet = Bullet()
bullet.rect.centerx = self.player.rect.centerx
bullet.rect.y = self.player.rect.y
# Add bullet to lists
all_sprites_list.add(self.bullet)
bullet_list.add(self.bullet)
That creates a new bullet every time the space bar is pressed. If your game design specifies a limit to the number of bullets that can be "active" at once, you may need some more complex logic (or if the performance cost of creating and destroying lots of instances is too much you could write some object caching code), but this should get you on the right track.
Now, the code above doesn't do anything to remove the bullets later, so you'll probably need to handle that too or your game will bog down from the calculations involving off-screen bullets. I'd suggest putting some logic in Bullet.update() that calls self.kill() if the bullet is off the screen (or whenever makes sense for your game). The instance will be garbage collected automatically when there are no more references to it.
I'd also suggest getting rid of all of the class variables of you Game class, which are either unnecessary (they get shadowed by instance variables that are created in __init__), or broken (like bullet).