Save TextInput on button press - kivy/python -

i have class button "save game", opens popup textinput widget , button save users text input. tried doesn't work. if print out filename after "modifying" it, prints out filename defined beforehand: .txt, not game1.txt or this.

class something(widget):     filename = ".txt"     # code game     def save(self,*args):         def on_text(instance, value):             return value          name = textinput(text="")         name.bind(text=on_text)         self.filename = "{}.txt".format(name.text)          b = boxlayout()         save_button = button(text="save file")         b.add_widget(save_button)         b.add_widget(name)         popup = popup(title="enter name:", content=b)          save_button.bind(on_release=popup.dismiss)         name.bind(on_text_validate=popup.on_dismiss) # wanted save when user closes popup         popup.open() 

where doing wrong? (i know won't save it, want create name here, have different class method saving it)