[Python] Can't properly modify a list in a for without It throwing error

I tried with [:] in lists but still doesn't work

for bullet in self.bullets[:]:
bullet.update(self.bullet_speed, self.bullets)
for obstacle in game.obstacle_manager.obstacles[:]:
if bullet.rect.colliderect(obstacle.rect):
game.obstacle_manager.obstacles.remove(obstacle)
self.bullets.remove(bullet)
bullet_flag = True
break
if bullet_flag:
break


it gets the error ValueError: list.remove(x): x not in list in self.bullets.remove(bullet)

I am looking for colision between bullets and obstacles if that happens the bullet and the obstacle should destroy

full function

def update(self, game):
bullet_flag = False
if game.player.type == WEAPON_TYPE:
if self.bullet_step%5 == 0:
self.bullets.append(Bullet(game.player))
self.bullet_step += 1
for bullet in self.bullets[:]:
bullet.update(self.bullet_speed, self.bullets)
for obstacle in game.obstacle_manager.obstacles[:]:
if bullet.rect.colliderect(obstacle.rect):
game.obstacle_manager.obstacles.remove(obstacle)
self.bullets.remove(bullet)
bullet_flag = True
break
if bullet_flag:
break


It seems that all answer point to use [:] so I hope you can help me since that didn't work or I'm not doing it right.
REVIEW: in

self.bullets.remove(bullet)


I'm doing It in the self.bullets[:] or in the original list? I guess here is the answer.
PS: Can't find the code.
REVIEW2 WITH MY FATHER: So got that I was modifying the original list bullets instead the one on the for

self.bullets[:]


So the solution will be to create a variable before the for

aux = self.bullets[:]


then modify It in the for and then assigning the original to the new bullets list

aux.remove(bullet)
self.bullets = aux


I honestly coulnd't think about It that's why I thought I could ask It anyway thanks everybody.
FINAL SOLUTION:

for bullet in aux:
bullet.update(self.bullet_speed, self.bullets)
for obstacle in game.obstacle_manager.obstacles[:]:
if bullet.rect.colliderect(obstacle.rect):
game.obstacle_manager.obstacles.remove(obstacle)
aux.remove(bullet)
bullet_flag = True
break
if bullet_flag:
break
self.bullets = aux

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