Boomerang implementing logic

[Piethon]

if now - self.last >= self.cooldown is true then its code will just counteract the one above
I think you meant to do this

def update(self):
    self.pos += self.vel * self.game.dt
    self.rect.center = self.pos
    if self.game.player.weapon == 'boomerang':
        now = pg.time.get_ticks()
        if now - self.last >= self.cooldown:
            self.pos -= self.vel * self.game.dt
        else:
            self.pos += self.vel * self.game.dt
        self.rect.center = self.pos

I did this and now it is flying the time of the cool down and then it just stands there and waits till it gets removed.
My update section is looking like this:

 def update(self):
        self.pos += self.vel * self.game.dt
        self.rect.center = self.pos
        if self.game.player.weapon == 'boomerang':
            now = pg.time.get_ticks()
            if now - self.last >= self.cooldown:
                self.pos -= self.vel * self.game.dt
            else:
                self.pos += self.vel * self.game.dt
            self.rect.center = self.pos
        if pg.sprite.spritecollideany(self, self.game.walls):
            self.kill()
        if pg.time.get_ticks() - self.spawn_time > WEAPONS[self.game.player.weapon]['lifetime']:
            self.kill()

What am I doing wrong?