Simple carousel example with Kivy using ScreenManager, doing automatic transitions.

carousel_shader.py

"""
Simple `ScreenManager` carousel with screen widgets and optionally, a
shader transition.

This `ScreenManager` changes its `Screen` widgets every 2 seconds (note
the `Clock.schedule_interval()` in `CarouselTest1.__init__()`.

Additional transitions can be triggered with the toggle button.
"""

from __future__ import print_function, unicode_literals
# import dbg_cfg
import kivy
kivy.require('1.10.0')
from kivy.clock import Clock
from kivy.uix.button import Button
from kivy.uix.floatlayout import FloatLayout
from kivy.app import App
from kivy.lang import Builder
from kivy.uix.screenmanager import ScreenManager, FadeTransition, WipeTransition
from kivy.logger import Logger

KV = '''
#:kivy 1.10.0

CarouselTest1:
    Screen:
        name: 'screen1'
        canvas:
            Color:
                rgba: 0.5, 1, 1, 0.5
            Rectangle:
                pos: self.pos
                size: self.size
    Screen:
        name: 'screen2'
        canvas:
            Color:
                rgba: 1, 0.5, 0.5, 0.5
            Rectangle:
                pos: self.pos
                size: self.size
'''

toggle_counter = 0

class CarouselTest1(ScreenManager):

    def __init__(self, **kwargs):
        super(CarouselTest1, self).__init__(**kwargs)
        Clock.schedule_interval(self._toggle, 2)

        ##########################
        # change transition here #
        ##########################

        # self.transition = WipeTransition()

    def _toggle(self, *_):
        global toggle_counter
        toggle_counter += 1
        if toggle_counter % 10 == 0:
            Logger.debug("Did {} transitions so far".format(toggle_counter))
        self.current = self.next()


class CarouselTest1App(App):

    def build(self):
        layout = FloatLayout()
        car_test = Builder.load_string(KV)
        layout.add_widget(car_test)
        layout.add_widget(Button(text='toggle', size_hint=(0.1,0.1),
                                 on_press=lambda *_:self.root.children[-1]._toggle()))
        return layout

if __name__ == '__main__':
    CarouselTest1App().run()

dbg_cfg.py

"""
Debug configuration for easy import (instead of env vars/config file).

Uncomment ``import dbg_cfg`` in the main file, to see debug output.
"""

# import os
# os.environ['KIVY_NO_CONFIG'] = '1'  # if active, no other config file is loaded

from kivy import Config
Config.set('kivy', 'log_level', 'debug')