It's mostly about communicating with subprocess and Popen, which has little to do with this article, other than being Python modules you can use with concurrent futures. It's also long-winded and beside the point. Shouldn't be the top comment.
Subprocessing is the only way to do full parallelism in Python. The title includes parallelism, and the article says how threading can achieve it specifically if your CPU-bound portion is inside C modules (which release the GIL), but it's relevant to mention how you do parallelism in the general case.
