kivy remove_widget not removing - button

Question

I'm learning about kivy and was playing around with the PONG example. I added a button that appears after a player reaches a given score.
if self.player2.score ==2 or self.player1.score==2:
self.serve_ball(vel=(0, 0))
self.btn= Button()
self.add_widget(self.btn)
self.btn.bind(on_press=self.callback)
It binds to a function callback that resets the score and messages but I've tried several things to remove the button after pressed with no success.
def callback(self, instance):
self.player2.score=0
self.player1.score=0
self.message1=""
self.message2=""
self.serve_ball(vel=(4,0))
self.remove_widget(self.btn)
Any ideas how? Thanks, this is the complete code
from kivy.app import App
from kivy.uix.widget import Widget
from kivy.uix.button import Button
from kivy.properties import StringProperty, NumericProperty, ReferenceListProperty, ObjectProperty
from kivy.vector import Vector
from kivy.clock import Clock
from random import randint
class PongPaddle(Widget):
score = NumericProperty(0)
def bounce_ball(self, ball):
if self.collide_widget(ball):
vx, vy = ball.velocity
offset = (ball.center_y - self.center_y) / (self.height / 2)
bounced = Vector(-1 * vx, vy)
vel = bounced * 1.1
ball.velocity = vel.x, vel.y + offset
class PongBall(Widget):
#Vel of ball in x & y axis
velocity_x = NumericProperty(0)
velocity_y = NumericProperty(0)
#referencia para usar como vector
velocity = ReferenceListProperty(velocity_x,velocity_y)
#funcion move 1 paso en intervalos para animar la bola
def move(self):
self.pos = Vector(*self.velocity) + self.pos
class PongGame(Widget):
ball = ObjectProperty(None)
player1 = ObjectProperty(None)
player2 = ObjectProperty(None)
message2 = StringProperty("")
message1 = StringProperty("")
def callback(self, instance):
self.player2.score=0
self.player1.score=0
self.message1=""
self.message2=""
self.serve_ball(vel=(4,0))
self.remove_widget(self.btn)
def serve_ball(self, vel=(4,0)):
self.ball.center = self.center
self.ball.velocity = vel
def btnn(self, instance):
self.remove_widget(self.btn)
def update(self, dt):
self.ball.move()
#bounce of paddles
self.player1.bounce_ball(self.ball)
self.player2.bounce_ball(self.ball)
#bounce ball off bottom or top
if (self.ball.y < self.y) or (self.ball.top > self.top):
self.ball.velocity_y *= -1
#went of to a side to score point?
if self.ball.x < self.x:
self.player2.score += 1
self.serve_ball(vel=(4, 0))
if self.ball.x > self.width:
self.player1.score += 1
self.serve_ball(vel=(-4, 0))
#emilio code
if self.player2.score ==2 or self.player1.score==2:
self.serve_ball(vel=(0, 0))
self.btn= Button()
self.add_widget(self.btn)
self.btn.bind(on_press=self.callback)
if self.player2.score == 2:
self.message2= "player2 won!"
if self.player1.score == 2:
self.message1= "player1 won!"
def on_touch_move(self, touch):
if touch.x < self.width / 3:
self.player1.center_y = touch.y
if touch.x > self.width - self.width / 3:
self.player2.center_y = touch.y
class PongApp(App):
def build(self):
game = PongGame()
game.serve_ball()
Clock.schedule_interval(game.update, 1.0 / 60.0)
return game
if __name__=='__main__':
PongApp().run()`
This is the kv file just in case:
#:kivy 1.0.9
<PongBall>:
size: 50, 50
canvas:
Ellipse:
pos: self.pos
size: self.size
<PongPaddle>:
size: 25, 200
canvas:
Rectangle:
pos:self.pos
size:self.size
<PongGame>:
ball: pong_ball
player1: player_left
player2: player_right
canvas:
Rectangle:
pos: self.center_x - 5, 0
size: 10, self.height
Label:
font_size: 70
center_x: root.width / 4
top: root.top - 50
text: str(root.player1.score)
color: (255,0,255,1)
Label:
font_size: 70
center_x: root.width * 3 / 4
top: root.top - 50
text: str(root.player2.score)
color: (255,0,255,1)
Label:
font_size: 40
center_x: root.width * 3/4
top: root.center_y
text: str(root.message2)
color: (0,255,0,1)
Label:
font_size: 40
center_x: root.width / 4
top: root.center_y
text: str(root.message1)
color: (0,255,0,1)
PongBall:
id: pong_ball
center: self.parent.center
PongPaddle:
id: player_left
x: root.x
center_y: root.center_y
PongPaddle:
id: player_right
x: root.width-self.width
center_y: root.center_y

Answer 1

The update function is called a lot of times and each time your condition is met you create another button. only to remove the last button created when you click at it...
Here is your bug:
if self.player2.score ==2 or self.player1.score==2:
print 'WOO' # see how many times this is gonna be printed
#make sure you don't get here more than once per game :)
self.serve_ball(vel=(0, 0))
self.btn= Button()
self.add_widget(self.btn)
self.btn.bind(on_press=self.callback)