here is my current program and there is a mistake about this program, please tell me how can i fix this??

Please enter the file_nane of the background image:background_inage_01.bmp how many ninjas(1-8) that you want add to the background image:8 Traceback (most recent call last): File "777.py", line 6, in (f, g) a.get..rect().size = AttributeError: 'str' object has no attribute 'get_rect