How do I use python to get the UI elements of a native mac app?

There is some information you can access about the windows and titles using the Python Quartz package, but it sounds like you want items rendered in the window. If it's just window info, use Quartz, here's the gist:

import Quartz
windows = Quartz.CGWindowListCopyWindowInfo( Quartz.kCGWindowListOptionAll, Quartz.kCGNullWindowID)
print windows[0].valueForKey_(kCGWindowBounds)
...

If you want the items rendered in the window, you'll need to be able to modify the child program so it sets NSWindow.sharingType = .readOnly. In addition, you'll most likely need to have spawned the child process. After all that, you may be able obtain a handle to the NSWindow using the CGWindowID:

 import AppKit
 windowID = windows[0].valueForKey_(kCGWindowNumber)
 window = NSWindow.windowWithWindowNumber(windowID)
 print window.contentView.subViews[0]
 ...

and introspect the NSWindow.contentView to find your target subview of type NSTextField, etc.

I haven't tried the second part using NSWindow.windowWithWindowNumber, but I have used the Quartz package in other projects successfully.

From what I remember from previous tries, pyatomac proved pretty useful. They have a quite good documentation.