Right, security implications are one of the reasons why I've held back from proposing Shell Command. The lack of cross platform support is also a pain. This suggestion shares both of those problems.

Having dealt with long running child processes lately, I can also say that producing output line-by-line would be on my personal list of requirements.

So, yeah, interesting idea, but this is still an area that needs a lot of exploration on PyPI before we select an answer for the stdlib.

--
Sent from my phone, thus the relative brevity :)