PYGAME : Why does calling a function inside the game loop inside Game loop make my game lag?

Question

I am making a simple game where enemies move around on the screen and we need to shoot them.I wanted to modularize my code so I wanted to replace the game loop logic with a function.But as soon as I do that, there's a drop in fps. Does calling a function inside while loop reduces the fps?

Without using functions,my game loop is:

while True:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            pygame.quit()
            sys.exit()
        if event.type == pygame.MOUSEBUTTONDOWN:
            crosshair.shoot()
    
        pygame.display.update()
        #blit bg
        displaysurf.blit(background,(0,0))
        #render group of sprites
        target_group.draw(displaysurf)
        crosshair_group.draw(displaysurf)
        #call the update methods
        crosshair_group.update()
        target_group.update()
        #display fps
        #print(clock.get_fps())
        #restrict to 60frames drawing per second
        clock.tick(60)

With the function:

def first_level():
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            pygame.quit()
            sys.exit()
        if event.type == pygame.MOUSEBUTTONDOWN:
            crosshair.shoot()
    
        pygame.display.update()
        #blit bg
        displaysurf.blit(background,(0,0))
        #render group of sprites
        target_group.draw(displaysurf)
        crosshair_group.draw(displaysurf)
        #call the update methods
        crosshair_group.update()
        target_group.update()
        #display fps
        #print(clock.get_fps())
        #restrict to 60frames drawing per second
        clock.tick(60)
while True: 
        first_level()

But the moment I add this function,my game starts to lag due to reduction in FPS.Why does this happen?

Answer 1

It looks like you messed up your indentation. pygame.display.update() and everything after that should not be part of the for event... loop.

def first_level():
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            pygame.quit()
            sys.exit()
        if event.type == pygame.MOUSEBUTTONDOWN:
            crosshair.shoot()
    
    pygame.display.update()
    #blit bg
    displaysurf.blit(background,(0,0))
    #render group of sprites
    target_group.draw(displaysurf)
    crosshair_group.draw(displaysurf)
    #call the update methods
    crosshair_group.update()
    target_group.update()
    #display fps
    #print(clock.get_fps())
    #restrict to 60frames drawing per second
    clock.tick(60)

while True: 
    first_level()