Вот без ui designer:
# coding: utf-8
import ui
def button_tapped(sender):
sender.title = 'Hello'
view = ui.View()
view.name = 'Demo'
view.background_color = 'white'
button = ui.Button(title='Tap me!')
button.center = (50, 25)
button.flex = 'LRTB'
button.action = button_tapped
button.background_color = 'green'
view.add_subview(button)
view.present('sheet')
По ui designer есть хорошая документация
omz-software.com/pythonista/docs/ios/ui.html#using...