How to make enemies move to the centre of screen? [duplicate] - pygame

Question

i'm learning python by myself, and started with a simple game with pygame.
The game consists, so far, in a ball that's been chased by other balls, i have created a loop that avoid the chasing balls to overlap.
The way the loop works its by a nested loop that moves thru a list that includes all the chasing balls, then measures the distance between them, if the distance is less than the ball radius, it is moved away.
It seems to work most of the time, but sometimes a ball overlaps. I dont know why, if anyone can take a look at my code and give me a hint i would apreciate it, i think the error happens when there are more than 3 balls and at the moment when the player's ball (pelota) collides.
import pygame, random, math
pygame.init()
ancho , alto = 800 , 600
negro = (0,0,0)
blanco=(255,255,255)
FPS = 60
velocidad = 7
velocidadnalguis = velocidad - 2
contadordecolisiones = 1
perseguidores = []
pantalla=pygame.display.set_mode((ancho,alto))
pygame.display.set_caption("un jueguito")
reloj=pygame.time.Clock()
class Pelota(pygame.sprite.Sprite):
def __init__(self):
pygame.sprite.Sprite.__init__(self)
self.image = pygame.image.load("pelota.png").convert()
self.image = pygame.transform.scale(self.image, (30, 30))
self.image.set_colorkey(negro)
self.rect = self.image.get_rect()
self.rect.center = (ancho/2,alto/2)
self.speed = 0
def update(self):
self.speedx = 0
self.speedy = 0
tecla = pygame.key.get_pressed()
if tecla[pygame.K_LEFT]:
self.speedx = -velocidad
if tecla[pygame.K_RIGHT]:
self.speedx = velocidad
if tecla[pygame.K_UP]:
self.speedy = -velocidad
if tecla[pygame.K_DOWN]:
self.speedy = velocidad
self.rect.x += self.speedx
self.rect.y += self.speedy
if self.rect.right > ancho:
self.rect.right = ancho
if self.rect.bottom > alto:
self.rect.bottom = alto
if self.rect.left < 0:
self.rect.left = 0
if self.rect.top < 0:
self.rect.top = 0
pelota = Pelota()
class Perseguidor(pygame.sprite.Sprite):
def __init__(self,):
super().__init__()
self.image = pygame.image.load('nalguis.png').convert()
self.image = pygame.transform.scale(self.image, (30, 30))
self.image.set_colorkey(negro)
self.rect = self.image.get_rect()
self.velocidad = velocidadnalguis
self.radius = self.rect.width/2
self.center = self.rect.center
self.contadordecolisiones = 1
self.enerandom = random.randint(0,4)
if self.enerandom == 0:
self.rect.center = (random.randrange(-130,-30),random.randrange(-130,alto+130))
if self.enerandom == 1:
self.rect.center = (random.randrange(-130,ancho+130),random.randrange(-130,-30))
if self.enerandom == 2:
self.rect.center = (random.randrange(ancho+30,ancho+130),random.randrange(-130,alto+130))
if self.enerandom == 3:
self.rect.center = (random.randrange(-130,ancho+130),random.randrange(alto+30,alto+130))
def update(self):
self.pely = pelota.rect.y
self.pelx = pelota.rect.x
self.perx = self.rect.x
self.pery = self.rect.y
self.dist = math.sqrt(((self.pely-self.pery)**2) + ((self.pelx-self.perx)**2))/velocidadnalguis
self.angulo = math.atan2(self.pely-self.pery,self.pelx-self.perx)
self.speedx = 0
self.speedy = 0
self.speedx = math.cos(self.angulo)
self.speedy = math.sin(self.angulo)
if self.dist>=1:
self.rect.x += velocidadnalguis * self.speedx
self.rect.y += velocidadnalguis * self.speedy
all_sprites = pygame.sprite.Group()
perseguidor_grupo = pygame.sprite.Group()
all_sprites.add(pelota)
terminar=False
while not terminar:
reloj.tick(FPS)
for event in pygame.event.get():
if event.type == pygame.QUIT:
terminar=True
if len(perseguidor_grupo)<1:
perseguidor=Perseguidor()
perseguidor_grupo.add(perseguidor)
all_sprites.add(perseguidor)
hit = pygame.sprite.spritecollide(pelota, perseguidor_grupo, True, pygame.sprite.collide_circle)
if hit:
if len(perseguidor_grupo)<25:
perseguidor = Perseguidor()
perseguidor1 = Perseguidor()
all_sprites.add(perseguidor, perseguidor1)
perseguidor_grupo.add(perseguidor, perseguidor1)
perseguidores.append(perseguidor1)
perseguidores.append(perseguidor)
else :
perseguidor = Perseguidor()
all_sprites.add(perseguidor)
perseguidor_grupo.add(perseguidor)
perseguidores.append(perseguidor)
dist=1
for i in range (len(perseguidores)):
for j in range(i+1,len(perseguidores)):
perseguidoresxy = [perseguidores[i].rect.centerx,perseguidores[i].rect.centery]
dist=math.hypot(perseguidores[i].rect.centerx - perseguidores[j].rect.centerx , perseguidores[i].rect.centery - perseguidores[j].rect.centery)
if dist <= perseguidor.radius*2:
if perseguidores[i].rect.centerx < perseguidores[j].rect.centerx:
perseguidores[i].rect.centerx -= 3
if perseguidores[i].rect.centery < perseguidores[j].rect.centery:
perseguidores[i].rect.centery -= 3
if perseguidores[i].rect.centerx > perseguidores[j].rect.centerx:
perseguidores[i].rect.centerx += 3
if perseguidores[i].rect.centery > perseguidores[j].rect.centery:
perseguidores[i].rect.centery -= 3
if len(perseguidores)> len(perseguidor_grupo):
del perseguidores [0]
all_sprites.update()
pantalla .fill(negro)
all_sprites.draw(pantalla)
pygame.display.flip()
pygame.quit()
quit()

Answer 1

[...] then measures the distance between them, if the distance is less than the ball radius, it is moved away. It seems to work most of the time, but sometimes a ball overlaps. [...]
Of course.You only consider 2 balls when moving a ball away.
This means that if you move a ball away from one ball, it can happen that you move it straight onto another ball.
You need to check that there is no other ball in the position where you are moving the ball.
Make sure the balls don't overlap as they spawn:
requested_balls = 1
while not terminar:
# [...]
hit = pygame.sprite.spritecollide(pelota, perseguidor_grupo, True, pygame.sprite.collide_circle)
if hit:
requested_balls = min(25, requested_balls+1)
if len(perseguidor_grupo) < requested_balls:
perseguidor = Perseguidor()
if not pygame.sprite.spritecollide(perseguidor, perseguidor_grupo, True, pygame.sprite.collide_circle):
all_sprites.add(perseguidor)
perseguidor_grupo.add(perseguidor)
perseguidores.append(perseguidor)
Only move a ball if the new position of the ball is not yet occupied by a ball:
class Perseguidor(pygame.sprite.Sprite):
# [...]
def update(self):
# [...]
old_rect = self.rect.copy()
if self.dist>=1:
self.rect.x += velocidadnalguis * self.speedx
self.rect.y += velocidadnalguis * self.speedy
hit = pygame.sprite.spritecollide(self, perseguidor_grupo, False, pygame.sprite.collide_circle)
if len(hit) > 1: # at last 1, because the ball hits itself
if random.randrange(2) == 0:
self.rect.x = old_rect.x
else:
self.rect.y = old_rect.y
hit = pygame.sprite.spritecollide(self, perseguidor_grupo, False, pygame.sprite.collide_circle)
if len(hit) > 1:
self.rect = old_rect
Complete example:
import pygame, random, math
pygame.init()
ancho , alto = 800 , 600
negro = (0,0,0)
blanco=(255,255,255)
FPS = 60
velocidad = 7
velocidadnalguis = velocidad - 2
contadordecolisiones = 1
perseguidores = []
pantalla=pygame.display.set_mode((ancho,alto))
pygame.display.set_caption("un jueguito")
reloj=pygame.time.Clock()
class Pelota(pygame.sprite.Sprite):
def __init__(self):
pygame.sprite.Sprite.__init__(self)
self.image = pygame.image.load("pelota.png").convert()
self.image = pygame.transform.scale(self.image, (30, 30))
self.image.set_colorkey(negro)
self.rect = self.image.get_rect()
self.rect.center = (ancho/2,alto/2)
self.speed = 0
def update(self):
self.speedx = 0
self.speedy = 0
tecla = pygame.key.get_pressed()
if tecla[pygame.K_LEFT]:
self.speedx = -velocidad
if tecla[pygame.K_RIGHT]:
self.speedx = velocidad
if tecla[pygame.K_UP]:
self.speedy = -velocidad
if tecla[pygame.K_DOWN]:
self.speedy = velocidad
self.rect.x += self.speedx
self.rect.y += self.speedy
if self.rect.right > ancho:
self.rect.right = ancho
if self.rect.bottom > alto:
self.rect.bottom = alto
if self.rect.left < 0:
self.rect.left = 0
if self.rect.top < 0:
self.rect.top = 0
pelota = Pelota()
class Perseguidor(pygame.sprite.Sprite):
def __init__(self,):
super().__init__()
self.image = pygame.image.load('nalguis.png').convert()
self.image = pygame.transform.scale(self.image, (30, 30))
self.image.set_colorkey(negro)
self.rect = self.image.get_rect()
self.velocidad = velocidadnalguis
self.radius = self.rect.width/2
self.center = self.rect.center
self.contadordecolisiones = 1
self.enerandom = random.randint(0,4)
if self.enerandom == 0:
self.rect.center = (random.randrange(-130,-30),random.randrange(-130,alto+130))
if self.enerandom == 1:
self.rect.center = (random.randrange(-130,ancho+130),random.randrange(-130,-30))
if self.enerandom == 2:
self.rect.center = (random.randrange(ancho+30,ancho+130),random.randrange(-130,alto+130))
if self.enerandom == 3:
self.rect.center = (random.randrange(-130,ancho+130),random.randrange(alto+30,alto+130))
def update(self):
self.pely = pelota.rect.y
self.pelx = pelota.rect.x
self.perx = self.rect.x
self.pery = self.rect.y
self.dist = math.sqrt(((self.pely-self.pery)**2) + ((self.pelx-self.perx)**2))/velocidadnalguis
self.angulo = math.atan2(self.pely-self.pery,self.pelx-self.perx)
self.speedx = 0
self.speedy = 0
self.speedx = math.cos(self.angulo)
self.speedy = math.sin(self.angulo)
old_rect = self.rect.copy()
if self.dist>=1:
self.rect.x += velocidadnalguis * self.speedx
self.rect.y += velocidadnalguis * self.speedy
hit = pygame.sprite.spritecollide(self, perseguidor_grupo, False, pygame.sprite.collide_circle)
if len(hit) > 1: # at last 1, because the ball hits itself
if random.randrange(2) == 0:
self.rect.x = old_rect.x
else:
self.rect.y = old_rect.y
hit = pygame.sprite.spritecollide(self, perseguidor_grupo, False, pygame.sprite.collide_circle)
if len(hit) > 1:
self.rect = old_rect
all_sprites = pygame.sprite.Group()
perseguidor_grupo = pygame.sprite.Group()
all_sprites.add(pelota)
terminar=False
requested_balls = 1
while not terminar:
reloj.tick(FPS)
for event in pygame.event.get():
if event.type == pygame.QUIT:
terminar=True
if len(perseguidor_grupo)<1:
perseguidor=Perseguidor()
perseguidor_grupo.add(perseguidor)
all_sprites.add(perseguidor)
hit = pygame.sprite.spritecollide(pelota, perseguidor_grupo, True, pygame.sprite.collide_circle)
if hit:
requested_balls = min(25, requested_balls+1)
if len(perseguidor_grupo) < requested_balls:
perseguidor = Perseguidor()
if not pygame.sprite.spritecollide(perseguidor, perseguidor_grupo, True, pygame.sprite.collide_circle):
all_sprites.add(perseguidor)
perseguidor_grupo.add(perseguidor)
perseguidores.append(perseguidor)
dist=1
if len(perseguidores)> len(perseguidor_grupo):
del perseguidores [0]
all_sprites.update()
pantalla .fill(negro)
all_sprites.draw(pantalla)
pygame.display.flip()
pygame.quit()
quit()