Kivy Does Not Output Plain Text, Only Object Location

问题

So I was trying to create a very basic text editor in Kivy. So I had got around the issue of text not showing up (via lambda). However, a new error appeared on the horizon; saving. I want to save automatically to a plain txt file. However, my current code only save an object (is it a pointer?) of the actual text input. Thank you all, SO!

    import kivy
    import os
    kivy.require('1.10.1') # replace with your current kivy version !
    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.clock import Clock
    from kivy.uix.button import Button
    from kivy.lang import Builder

    class ColdKivyApp(App): # I actually used to call it Zone but changed it to Cold cause it's cold outside ;)
            def build(self):
                    f = BoxLayout(orientation='vertical')
                    txt = TextInput(multiline=True, cursor_blink=True, background_color=(1,1,1,1))
                    f.add_widget(txt)
                    txtstr = str(txt)
                    Clock.schedule_once(lambda *args: setattr(txt, "focus", True))
                    with open('testtxt.txt', 'w') as txtwriter:
                        txtwriter.write("" + txtstr)
                        txtwriter.close()
                    return f

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

Edit: Spelling