import easygui

choices = ['opt 1', 'opt2']
answer = easygui.choicebox('text', 'title', choices=choices)
if answer == 'opt 1':
  easygui.msgbox('text', 'title', ok_button="ok button")
elif answer == 'opt2':
  choices = ['opt1', 'opt 2']
  easygui.choicebox('text', 'title', choices=choices)