Issue running functions in pygame

Question

import pygame
import random
import time

pygame.init()
backX = 1000
backY = 600
screen = pygame.display.set_mode((backX, backY))

score = 0
white = (255, 255, 255)
green = (0, 255, 0)
blue = (0, 0, 128)
timespent = 0
pygame.display.set_caption('Monkey Simulator')  # game name
pygame.font.init()  # you have to call this at the start,
# if you want to use this module.
myfont = pygame.font.SysFont('Comic Sans MS', 30)
textsurface = myfont.render('Score: ' + str(score), False, (255, 255, 255))
pygame.mixer.init()
# music
sound = pygame.mixer.Sound('background1.mp3')
collection = pygame.mixer.Sound('collection.mp3')
gameover1 = pygame.mixer.Sound('gameover.mp3')
sound.play(-1)
# score indicator
text = myfont.render('Score: ' + str(score), True, white, blue)

textRect = text.get_rect()  # getting the rectangle for the text object

textRect.center = (400 // 2, 400 // 2)
pre_background = pygame.image.load('background.jpeg')

background = pygame.transform.scale(pre_background, (backX, backY))
clock = pygame.time.Clock()
FPS = 60
vel = 6.5
BLACK = (0, 0, 0)
monkeyimg = pygame.image.load('monkey.png')
playerX = 410
playerY = 435
bananavelocity = 4
monkey = pygame.transform.scale(monkeyimg, (100, 120))
prebanana = pygame.image.load('banana.png')
bananaXList = []
def change():
    if score>=5:
        monkey = pygame.transform.scale(pre_shark, (100, 100))
        banana = pygame.transform.scale(pre_meat, (50, 50))
        background = pygame.transform.scale(underwater, (backX, backY))
for i in range(50):
    value = random.randint(10, 980)
    bananaXList.append(value)
valuenumber = random.randint(1, 30)
bananaX = bananaXList[valuenumber - 1]
bananaY = 0
banana = pygame.transform.scale(prebanana, (50, 50))
underwater = pygame.image.load('underwater.jpg')
pre_shark = pygame.image.load('shark.png')
pre_meat = pygame.image.load('meat.png')
banana_rect = banana.get_rect(topleft=(bananaX, bananaY))
monkey_rect = monkey.get_rect(topleft=(playerX, playerY))
run = True
black = (0, 0, 0)

    # start screen
screen.blit(background, (0, 0))
myfont = pygame.font.SysFont("Britannic Bold", 50)
end_it = False

while not end_it:
    myfont1 = pygame.font.SysFont("Britannic Bold", 35)

    nlabel = myfont.render("Monkey Simulator", 1, (255, 255, 255))
    info = myfont1.render("Use your right and left arrow keys to move the character.", 1, (255, 255, 255))
    info2 = myfont1.render("Try to catch as many bananas as you can while the game speeds up!", 1, (255, 255, 255))

    for event in pygame.event.get():
        if event.type == pygame.MOUSEBUTTONDOWN:
            end_it = True
    screen.blit(nlabel, (400, 150))
    screen.blit(info, (100, 300))
    screen.blit(info2, (100, 350))

    pygame.display.flip()

while run:
    clock.tick(FPS)
    screen.fill(BLACK)
    screen.blit(background, (0, 0))
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            run = False
    keys = pygame.key.get_pressed()
    # banana animation
    bananaY = bananaY + bananavelocity
    timespent = int(pygame.time.get_ticks() / 1000)
    bananavelocity = 4 + (timespent * 0.055)
    vel = 6.5 + (timespent * 0.07)
    # end game sequence
    change()
    if bananaY > 510:
        bananaX = -50
        bananaY = -50
        banana

        velocity = 0
        gameover = pygame.image.load("gameover.jpg")
        background = pygame.transform.scale(gameover, (backX, backY))
        pygame.mixer.Sound.stop(sound)
        gameover1.play()

    # collecting coins sequence
    if banana_rect.colliderect(monkey_rect):
        collection.play()
        valuenumber = random.randint(1, 30)
        bananaX = bananaXList[valuenumber - 1]
        bananaY = -25
        score += 1

    # moving character
    if keys[pygame.K_LEFT] and playerX > 0:
        playerX = playerX - vel
    if keys[pygame.K_RIGHT] and playerX < 930:
        playerX = playerX + vel
    # adding the sprites to the screen
    screen.blit(monkey, (playerX, playerY))
    screen.blit(banana, (bananaX, bananaY))
    banana_rect = banana.get_rect(topleft=(bananaX, bananaY))
    monkey_rect = monkey.get_rect(topleft=(playerX, playerY))
    pygame.draw.rect(screen, (150, 75, 0), pygame.Rect(0, 534, 1000, 20))
    screen.blit(textsurface, (30, 0))
    textsurface = myfont.render('Score: ' + str(score), False, (255, 255, 255))

    pygame.display.update()

Right now I'm making a collection game. I want to use a function for replacing all the images once you hit a certain score. It doesn't work, though, no matter how high of a score you get. I don't understand the issue because I tested both the function and the if statement by putting print statements.

Answer 1

You have to use the global statement when you want to change a variable in the global namespace within a function:

def change():
    global monkey, banana, background 
  
    if score>=5:
        monkey = pygame.transform.scale(pre_shark, (100, 100))
        banana = pygame.transform.scale(pre_meat, (50, 50))
        background = pygame.transform.scale(underwater, (backX, backY))

If you don't use the global statement, the values are assigned to local variables in the scope of the function.

---

Another option is to return the new values from the function:

def change():
    if score>=5:
        return ( 
            pygame.transform.scale(pre_shark, (100, 100)),
            pygame.transform.scale(pre_meat, (50, 50)),
            pygame.transform.scale(underwater, (backX, backY)) )
    return monkey, banana, background  

while True:
    # [...]

    monkey, banana, background = change()