Cannot shoot more than one projectile

Question

Shooting one bullet works but i can only shoot one and after that it stops working. I've tried to change my "bullet_fire" to False after KEYUP but this doesnt work either since then the bullet is only visible while i hold the arrow up key while the problem remain. How should i solve this problem? Here is the code:

import pygame

pygame.init()

# Skärm
Screen = pygame.display.set_mode((1600, 900))

# Title och Logo
pygame.display.set_caption("Fjärt Spel")
icon = pygame.image.load('planet.png')
pygame.display.set_icon(icon)

# backround
backround = pygame.image.load("0000.png")

# player
playerIMG = pygame.image.load("soldier.png")
playerX = 350
playerY = 836

playerX_Change = 0
playerY_Change = 30

# enemy
enemyIMG = pygame.image.load("terrorist2.png")
enemyX = 500
enemyY = 810

enemyX_Change = 0
enemyY_Change = 0

# bullet

bulletIMG = pygame.image.load("pung(32x32).png")
bulletX = playerX
bulletY = playerY

bulletX_Change = 50
bulletY_Change = 0
bullet_fire = False


offScreen = 1600, 900


def player(x, y):
    Screen.blit(playerIMG, (x, y))


def enemy(x, y):
    Screen.blit(enemyIMG, (x, y))



Running = True
while Running:

    Screen.fill((0, 0, 0))
    # backround
    Screen.blit(backround, (0, 0))

    if bullet_fire == True:
        Screen.blit(bulletIMG, (bulletX + 100, playerY))
        bulletX += bulletX_Change
    if bulletX > 1600:
        bullet_fire == False


    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            Running = False

        if event.type == pygame.KEYDOWN:
            if event.key == pygame.K_LEFT:
                playerX_Change = -10
            if event.key == pygame.K_RIGHT:
                playerX_Change = 10
            if event.key == pygame.K_SPACE:
                playerY_Change = -70
            if event.key == pygame.K_UP:
                bullet_fire = True



        if event.type == pygame.KEYUP:
            if event.key == pygame.K_LEFT or event.key == pygame.K_RIGHT or event.key == pygame.K_SPACE:
                playerX_Change = 0
                playerY_Change = 30




    # Ha player innan fill!!
    playerX += playerX_Change
    playerY += playerY_Change

    if playerX <= 0:
        playerX = 0
    elif playerX >= 1436:
        playerX = 1436
    if playerY <= 0:
        playerY = 0
    elif playerY >= 836:
        playerY = 836




    player(playerX, playerY)
    enemy(enemyX, enemyY)

    pygame.display.update()

Answer 1

if bulletX > 1600:
    bullet_fire == False
#               ^^

This appears to want to set bullet_fire to False when it reaches a certain ordinate but, in reality, is comparing the two and throwing away the result. That means the first bullet you've fired is still going, has left the screen, and is probably halfway to Jupiter by now :-)

By way of example, this is similar to the following transcript:

>>> a = 7
>>> if a == 7:
...     a == 14
...     print(a)
...
False
7

You need to use == for comparison and = for assignment.

---

Keep in mind that's the likely cause of your issue. Since your question does not contain the code that decides whether a new bullet should be generated, it's a little hard to tell for sure. I'm therefore basing it on the assumption that one bullet at a time is all that's permitted (as in quite a few arcade games). Hence, if you never "destroy" the current bullet, you'll never be able to fire another one.

If that turns out to not be the case, you probably need to post more code so we can do an exhaustive analysis.

---

As an aside, I'm a little concerned about the physics involved in:

Screen.blit(bulletIMG, (bulletX + 100, playerY))

This appears to draw the bullet at the players current Y position meaning that, after the bullet is fired, it will track the player in some weird Einsteinian "spooky action at a distance" manner. While that makes the game a lot easier since you can direct the bullets after firing, I'm not convinced it will get a high score in the realism category :-)