Why doesn't kivy find the function?

Question

Python

have python 3 code running on windows 10

import kivy
from kivy.app import App

class IdeApp(App):
  def printer():
    return 'pechat'

IdeApp().run()

there is a code for kv (file name ide.kv)

BoxLayout:
  Label:
    id: hell
    text: 'hello'
  Button:
    text: 'press me'
    on_press: hell.text = IdeApp.printer()

And when you click on the button, it gives an error like this.

Traceback (most recent call last):
   File "ide.py", line 8, in <module>
     IdeApp().run()
   File "C:\Python34\lib\site-packages\kivy\app.py", line 828, in run
     runTouchApp()
   File "C:\Python34\lib\site-packages\kivy\base.py", line 487, in runTouchApp
     EventLoop.window.mainloop()
   File "C:\Python34\lib\site-packages\kivy\core\window\window_sdl2.py", line 619, in mainloop
     self._mainloop()
   File "C:\Python34\lib\site-packages\kivy\core\window\window_sdl2.py", line 362, in _mainloop
     EventLoop.idle()
   File "C:\Python34\lib\site-packages\kivy\base.py", line 330, in idle
     self.dispatch_input()
   File "C:\Python34\lib\site-packages\kivy\base.py", line 315, in dispatch_input
     post_dispatch_input(*pop(0))
   File "C:\Python34\lib\site-packages\kivy\base.py", line 221, in post_dispatch_input
     listener.dispatch('on_motion', etype, me)
   File "kivy\_event.pyx", line 718, in kivy._event.EventDispatcher.dispatch (kivy\_event.c:7699)
   File "C:\Python34\lib\site-packages\kivy\core\window\__init__.py", line 1030, in on_motion
     self.dispatch('on_touch_down', me)
   File "kivy\_event.pyx", line 718, in kivy._event.EventDispatcher.dispatch (kivy\_event.c:7699)
   File "C:\Python34\lib\site-packages\kivy\core\window\__init__.py", line 1046, in on_touch_down
     if w.dispatch('on_touch_down', touch):
   File "kivy\_event.pyx", line 718, in kivy._event.EventDispatcher.dispatch (kivy\_event.c:7699)
   File "C:\Python34\lib\site-packages\kivy\uix\widget.py", line 432, in on_touch_down
     if child.dispatch('on_touch_down', touch):
   File "kivy\_event.pyx", line 718, in kivy._event.EventDispatcher.dispatch (kivy\_event.c:7699)
   File "C:\Python34\lib\site-packages\kivy\uix\behaviors\button.py", line 110, in on_touch_down
     self.dispatch('on_press')
   File "kivy\_event.pyx", line 714, in kivy._event.EventDispatcher.dispatch (kivy\_event.c:7654)
   File "kivy\_event.pyx", line 1224, in kivy._event.EventObservers.dispatch (kivy\_event.c:13497)
   File "kivy\_event.pyx", line 1108, in kivy._event.EventObservers._dispatch (kivy\_event.c:12329)
   File "C:\Python34\lib\site-packages\kivy\lang.py", line 1557, in custom_callback
     exec(__kvlang__.co_value, idmap)
   File ".\ide.kv", line 7, in <module>
     on_press: hell.text = Ide.printer()
 NameError: name 'Ide' is not defined

Why?

Answer 1

class IdeApp(App):
  def printer():
    return 'pechat'

IdeApp().run()

Doesn't start, Traceback:

class IdeApp():
  def printer():
    return 'pechat'

IdeApp().run()

How did it get started for you?
Well, this is how something worked...

class IdeApp():
    def printer():
        return 'pechat'

IdeApp()

Then you have:
and Traceback:
PS Not special, but it became interesting)