title: How to set a height to some buttons of GridLayout in Kivy Python?
body: <p>I'm working in an app with kivy and I have an issue that involve the <code>GridLayout</code>. I have a screen with different rows and I want the buttons of the last row to have always the same <code>height</code> (11,1% of the height of the Screen). I have tried to modify the attribute height in the buttons but doesn't work properly. With <code>size_hint_y</code> works fine , but the fact is that i want to do with <code>height</code> because the screen won't have always the same number of rows (is responsive and it depends of the selections of previous screens). I attach here the code that I've done with the attribute height calculated through the command <code>Window.height/9</code>:</p>
  
  <pre><code>from kivy.app import App
  from kivy.uix.label import Label
  from kivy.uix.gridlayout import GridLayout
  from kivy.uix.textinput import TextInput
  from kivy.uix.button import Button
  from kivy.uix.screenmanager import ScreenManager, Screen
  from kivy.core.window import Window
  
  
  class LoginScreen(GridLayout):
      def __init__(self,**kwargs):
          super(LoginScreen, self).__init__(**kwargs)
          self.cols=2
          self.add_widget(Label(text='Subject'))
          self.add_widget(Label(text=''))
          self.add_widget(Label(text='1'))
          self.add_widget(TextInput(multiline=False))
          self.add_widget(Label(text='2'))
          self.add_widget(TextInput(multiline=False))
          self.add_widget(Label(text='3'))
          self.add_widget(TextInput(multiline=False))
          self.add_widget(Label(text='4'))
          self.add_widget(TextInput(multiline=False))
          b1=Button(text='Exit',background_color=[0,1,0,1],height=int(Window.height)/9.0) #doesn't work properly 
          self.add_widget(b1)
          b2=Button(text='Run',background_color=[0,1,0,1],height=int(Window.height)/9.0) #doesn't work properly
          self.add_widget(b2)
          b1.bind(on_press=exit) 
  
  
  
  
  class SimpleKivy(App):
      def build(self):
          return LoginScreen()
  
  
  if __name__=='__main__':
      SimpleKivy().run()
  </code></pre>
  
  <p>I know it could be done with kivy language in a easier way but for my app is better to do in this way. If anyone knows how to fix this problem I would be very grateful. </p>