[Tutor] How to interact with the result of subprocess.call()

[Jim Byrnes]

subprocess.call(['libreoffice', '/home/jfb/test.ods'])
k.tap_key(k.enter_key)
k.tap_key(k.enter_key)

If I run the above code, libreoffice opens the test.ods spreadsheet then 
just sits there. When I close libreoffice the two enter_keys are 
executed in the terminal that originated the script.

How can I continue to send keystrokes to libreoffice from the script 
once it has been opened by subprocess.call()?

Thanks,  Jim