kivy, not working yet

generator.kv

BoxLayout:
    orientation: 'horizontal'

    TextInput:
        id: p0
 
    TextInput:
        id: p1
 
    Label:
        id: g0
 
    Button:
        id: c0
        on_release: copy()

main.py

#!/usr/bin/env python
from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.textinput import TextInput
from kivy.uix.label import Label
from kivy.uix.button import Button

layout = BoxLayout()

pass0  = TextInput(text="<initial passphrase0>")
layout.add_widget(pass0)

pass1  = TextInput(text="<initial passphrase1>")
layout.add_widget(pass1)

gen0 = Label(text="<generated passphrase>")
layout.add_widget(gen0)

button0 = Button(text="Copy to clipboard")
layout.add_widget(button0)


def copy(self):
   gen0.text = "cp: " + pass0.text + pass1.text

def on_more_text(instance, value):
   gen0.text = pass0.text + pass1.text
    
         
pass1.bind(text=on_more_text)

class GeneratorApp(App):
    def build(self):
        return layout
    #pass

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