What is the best way to create multiple bullets in Python using Pygame?

Question

I just started studying Python two days ago, so my code is sloppy...But I'm just trying to get something that works. I'm working on a simple shmup. I'm trying to get bullets to fire by holding down on the Z key...The problem I'm facing at the moment is getting multiple bullets to work correctly. No matter what I do, after five are shot, I can't shoot anymore. When I only had one bullet, I couldn't shoot it anymore if I was still holding down the Z key when the object state changed to remove it. Here's my code...

#!/usr/bin/python

import sys, pygame
pygame.init() 

windowSize = width, height = 640, 480
screen = pygame.display.set_mode((windowSize))
pygame.display.set_caption("rzrscm")
clock = pygame.time.Clock()

background = pygame.Surface(screen.get_size())
background = background.convert()

image = pygame.image.load("image.png")
Font = pygame.font.Font("font.ttf",12)
text = Font.render("PIXELFUCKER",1,(255,255,255))
textpos = text.get_rect(centerx=background.get_width()/2)

pygame.mixer.music.load("music.xm")
pygame.mixer.init(44100, -16, 1, 1024)
pygame.mixer.music.play(-1,0.0)

quit = False

eX = 0
eY = 50
dotState = 1

bullet1 = 0
bullet2 = 0
bullet3 = 0
bullet4 = 0
bullet5 = 0

shot = 0
wait = 0

x = 300
y = 300
pX = 0
pY = 0

while quit == False:

    background.fill((0,0,0))

    x += pX
    if x < 0 or x > 640:
        x -= pX
    if x == eX and y == eY:
    x -= pX
    y += pY
    if y < 0 or y > 480:
        y -= pY

    wait = wait + 1

    if shot == 1:     
        if bullet1 == 0 and bullet5 == 0:
            bullet1 = 1
            wait = 0
        if bullet1 == 1 and bullet2 == 0 and wait == 25:
            bullet2 = 1
            wait = 0
        if bullet2 == 1 and bullet3 == 0 and wait == 25:
            bullet3 = 1
            wait = 0
        if bullet3 == 1 and bullet4 == 0 and wait == 25:
            bullet4 = 1
            wait = 0
        if bullet4 == 1 and bullet5 == 0 and wait == 25:
            bullet5 = 1
            wait = 0

    if dotState != 3:  
        background.set_at((eX, eY),(255,255,255))
    if eX == 640:
        dotState = 2
    if eX == 0:
        dotState = 1
    if dotState == 1:
        eX = eX + 1
    if eX == x and eY == y:
    eX = eX - 1
    if dotState == 2:       
        eX = eX - 1
    if eX == x and eY == y:
    eX = eX + 1  

    if bullet1 == 0:
        bX = x
        bY = y
    if bullet1 == 1:
    bY = bY - 5
    background.set_at((bX, bY),(255,255,255)) 
    if bY == 0:
    bullet1 = 0
    if bY == eY and bX == eX:
        bullet1 = 0
        dotState = 3
    if bullet2 == 0:
        bX2 = x
        bY2 = y
    if bullet2 == 1:
    bY2 = bY2 - 5
    background.set_at((bX2, bY2),(255,255,255)) 
    if bY2 == 0:
    bullet2 = 0
    if bY2 == eY and bX2 == eX:
        bullet2 = 0
    if bullet3 == 0:
        bX3 = x
        bY3 = y
    if bullet3 == 1:
    bY3 = bY3 - 5
    background.set_at((bX3, bY3),(255,255,255)) 
    if bY3 == 0:
    bullet3 = 0
    if bY3 == eY and bX3 == eX:
        bullet3 = 0
        dotState = 3
    if bullet4 == 0:
        bX4 = x
        bY4 = y
    if bullet4 == 1:
    bY4 = bY4 - 5
    background.set_at((bX4, bY4),(255,255,255)) 
    if bY4 == 0:
    bullet4 = 0
    if bY4 == eY and bX4 == eX:
        bullet4 = 0
        dotState = 3
    if bullet5 == 0:
        bX5 = x
        bY5 = y
    if bullet5 == 1:
    bY5 = bY5 - 5
    background.set_at((bX5, bY5),(255,255,255)) 
    if bY5 == 0:
    bullet5 = 0
    if bY5 == eY and bX5 == eX:
        bullet5 = 0
        dotState = 3

background.set_at((x, y),(255,255,255))
background.blit(text,textpos)
screen.blit(background,(0,0))  

pygame.display.flip()
clock.tick(250) 

for event in pygame.event.get(): 
    if event.type == pygame.QUIT: 
        sys.exit(0)

    if event.type == pygame.KEYDOWN and event.key == pygame.K_LEFT:
        pX -= 2
    if event.type == pygame.KEYDOWN and event.key == pygame.K_RIGHT:
        pX += 2
    if event.type == pygame.KEYDOWN and event.key == pygame.K_UP:
        pY -= 2
    if event.type == pygame.KEYDOWN and event.key == pygame.K_DOWN:
        pY += 2       

    if event.type == pygame.KEYUP and event.key == pygame.K_LEFT:
        pX += 2
    if event.type == pygame.KEYUP and event.key == pygame.K_RIGHT:
        pX -= 2
    if event.type == pygame.KEYUP and event.key == pygame.K_UP:
        pY += 2
    if event.type == pygame.KEYUP and event.key == pygame.K_DOWN:
        pY -= 2       

    if event.type == pygame.KEYDOWN and event.key == pygame.K_z:
        shot = 1
    if event.type == pygame.KEYUP and event.key == pygame.K_z:
        shot = 0

Answer 1

Your code was a little hard to follow for me -- I'm fairly new to programming myself. However, I do have a few suggestions that might help a little.

First, you seem to be hardcoding in the coordinates of your bullets (ie bullet1, bullet2, and bX1, bY1 etc.). Because you seem to be unable to fire more then 5 bullets, I'm assuming that you're not resetting your bullets' x and y coordinates, along with other variables related to them to zero after it moves off the screen or something.

Also, try implementing your bullets as a class and put all your bullets in a list so you can have more then 5. This way, you can neatly encapsulate all the data you need for a single bullet so you can do things like bullet1.x = 3 or bullets_array[1].y = 3 instead of bX1 = 3.

(btw, I see you started learning Python just recently. I highly suggest you learn about lists, objects, and object-oriented programming (often abbreviated OOP). And dictionaries. They'll be your new best friends. OOP might be a little difficult to grok at first (at least, it was for me), but it'll be worth it.)

For example,

# snip initialization, etc.

class Bullet():
    def __init__(self, surface, x_coord, y_coord):
        self.surface = surface
        self.x = x_coord
        self.y = y_coord
        return

    def update(self, y_amount=5):
        self.y += y_amount
        self.surface.set_at((self.x, self.y),(255,255,255))
        return

bullets_array = []

# snip 

while quit == false:    # Inside the main loop...
    for event in pygame.event.get():
        #snip
        if event.type == pygame.KEYDOWN and event.key == pygame.K_z:
            bullets_array.append(background, player_x, player_y)

    #snip

    for bullet in bullets_array:
        bullet.update()
        # ...and check if the bullet is off the screen.
        # If so, remove it from the array.

If you want something a bit more complicated, try using Pygame's Sprite and Group classes.

http://pygame.org/docs/ref/sprite.html

Basically, instead of creating the Bullet class yourself, you base it on pygame.sprite.Sprite, implement whatever methods you need, then add it to a group (pygame.sprite.Group). That way would probably be more flexible.