Explanation of this Python language feature? [x for x in x for x in x] (to flatten a nested list)

[Chris Angelico]

On Sat, Apr 5, 2014 at 11:00 AM, Steven D'Aprano
<steve+comp.lang.python at pearwood.info> wrote:
> As I said, some of these may be abandoned, obsolete, experimental, or
> even vapourware. Some are probably just ports of CPython to another
> platform rather than completely independent implementations.

Python for OS/2 is definitely just a port. It's built from as close to
unmodified sources as possible, and doesn't (deliberately) add/remove
any features or anything. On the other hand, there's a Python for
Android which may be a separate project. (Or is that the Py4A you
referred to?)

ChrisA