really simple question from newbie - change button text on press

[MFD]

I'm trying to learn Kivy and am still relatively new to python. I'm trying to just make the text on a button change after it's pressed. I found this old entry

https://groups.google.com/forum/#!searchin/kivy-users/a.bind(on_press$3Dlambda/kivy-users/0RraFO6K_pE/F8pnXC6hG38J

but the code doesn't work. 

I feel like the original line the responder suggested should be in there

a.bind(on_press=lambda *args: args[0].text = 'Opened')

At least something that tells the text to change.

Here is the code:

#button press

import kivy
from kivy.app import App
from kivy.uix.button import Button
from kivy.uix.label import Label

class MyApp(App):
def build(self):
a = Button(text='unpressed')

a.bind(on_press=lambda *args: (args[0].setter('text'))

return a

if __name__ == '__main__':

    MyApp().run()

I get:

SyntaxError: invalid syntax
user$ kivy button_press.py 
  File "button_press.py", line 14
    return a
         ^

SyntaxError: invalid syntax

Thank you!!

[ZenCODE]

Think you have a tabs and spaces/indentation there issue. Either way, this is what I would suggest :-)

import kivy
from kivy.app import App
from kivy.uix.button import Button
from kivy.uix.label import Label

class MyApp(App):
    def build(self):
        a = Button(text='unpressed')

        def change_text(button):
            button.text = 'Changed'

        a.bind(on_press=change_text)