fixedCode

from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.properties import (ObjectProperty, ListProperty, StringProperty,
NumericProperty)
from kivy.factory import Factory
import random
from kivy.graphics import Color, Ellipse
from kivy.clock import Clock
from kivy.lang import Builder

kv = '''
Snowing:
    canvas.before:
        Color:
            rgb: [0.2, 0.2, 0.2]
        Ellipse:
            pos: self.pos
            size: self.size
'''

class Snowing(BoxLayout):
    FLAKE_SIZE = 5
    NUM_FLAKES = 60
    FLAKE_AREA = FLAKE_SIZE * NUM_FLAKES
    FLAKE_INTERVAL = 1.0 / 30.0

    def __init__(self, **kwargs):
        super(Snowing, self).__init__(**kwargs)
        self.flakes = [[x * self.FLAKE_SIZE, 0]
            for x in range(self.NUM_FLAKES)]
        Clock.schedule_interval(self.update_flakes, self.FLAKE_INTERVAL)

    def update_flakes(self, time):
        for f in self.flakes:
            f[0] += random.choice([-1, 1])
            f[1] -= random.randint(0, self.FLAKE_SIZE)
            if f[1] <= 0:
                f[1] = random.randint(0, int(self.height))

        self.canvas.before.clear()
        with self.canvas.before:
            widget_x = self.center_x - self. FLAKE_AREA / 2
            widget_y = self.pos[1]
            for x_flake, y_flake in self.flakes:
                x = widget_x + x_flake
                y = widget_y + y_flake
                Color(0.9, 0.9, 1.0)
                Ellipse(pos=(x, y), size=(self.FLAKE_SIZE, self.FLAKE_SIZE))


class SnowfallApp(App):
    def build(self):
        return Builder.load_string(kv)

if __name__ == '__main__':
    SnowfallApp().run()