My game character only moves when the mouse moves on the screen while it needs a mouse

I just start learning pygame, the problem is : the game character that I'm making is moving when mouse is moving in screen even though I don't need to use mouse and I need help with it. I added some code for bullets this part is not important for me now because the space ship is not moving without moving mouse in screen .

import pygame
from pygame.locals import*

#define fps
clock = pygame.time.Clock()
fps=60


screen_width = 600
screen_height = 800

screen = pygame.display.set_mode((screen_width,screen_height))
pygame.display.set_caption(' space invaders')

#colors
red=(255,0,0)
green=(0,255,0)


#load image
bg = pygame.image.load("img/bg.png")

def draw_bg():
    screen.blit(bg,(0,0))




#create spaceship class
class Spaceship(pygame.sprite.Sprite):
    def __init__(self,x,y,health):
        pygame.sprite.Sprite.__init__(self)
        self.image = pygame.image.load("img/spaceship.png")
        self.rect = self.image.get_rect()
        self.rect.center = [x, y]
        self.health_start = health
        self.health_remaining = health
        self.last_shot = pygame.time.get_ticks()

    def update(self):
        #set movement speed
        speed=8

        #get key press
        key=pygame.key.get_pressed()
        if key[pygame.K_LEFT] and self.rect.left>0:
            self.rect.x-=speed

        if key[pygame.K_RIGHT] and self.rect.right<screen_width:
            self.rect.x+=speed

        time_now=pygame.time.get_ticks()

        #shoot

        if key[pygame.K_SPACE]:
            bullet = Bullet(self.rect.centerx,self.rect.top)

            bullet_group.add(bullet)
            
        pygame.mouse.get_pos()



        #draw health bar
        pygame.draw.rect(screen,red,(self.rect.x,(self.rect.bottom+10),self.rect.width,15))
        
        if self.health_remaining>0:
            pygame.draw.rect(screen,green,(self.rect.x,(self.rect.bottom+10),int(self.rect.width*(self.health_remaining / self.health_start)),15))



#create Bullets class
class Bullets(pygame.sprite.Sprite):
    def __init__(self,x,y):
        pygame.sprite.Sprite.__init__(self)
        self.image=pygame.image.load("img/bullet.png")
        self.rect = self.image.get_rect()
        self.rect.center=[x,y]
    
    def update(self):
        self.rect.y-=5




# sprite groups   
spaceship_group = pygame.sprite.Group()
bullet_group=pygame.sprite.Group()




#create player
spaceship=Spaceship(int(screen_width / 2),screen_height-100 ,3)
spaceship_group.add(spaceship)


run = True
while run:
    clock.tick(fps)
    draw_bg()

    #events 
    for event in pygame.event.get():
        if event.type==pygame.QUIT:
            run=False

        #update spaceship
        spaceship.update()

        update bullets
        bullet_group.update()

        
        spaceship_group.draw(screen)
        bullet_group.draw(screen)


        pygame.display.update()
        
pygame.quit