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

[Chris Angelico]

On Fri, Mar 28, 2014 at 7:54 AM, Mark H Harris <harrismh777 at gmail.com> wrote:
> Some people equate developer with programmer with software engineer. This
> ought not be done, in my view. There are *many* programmers out there who
> suck at software engineering (and they are not computer scientists).  They
> also do not qualify as developers.

And this is the bit where, I think, we disagree. I think that
programming is for programmers, in the same way that music is for
musicians and the giving of legal advice is for lawyers. Yes, there
are armchair lawyers, and plenty of people can pick up a hymn book and
sing; but laws and operas aren't designed with them in mind. Why
should programming languages be designed for the people who don't want
to learn them?

ChrisA