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 4:02 PM, Mark H Harris <harrismh777 at gmail.com> wrote:
>    I know its just a gut feel, and I know there are a lot of lurkers here
> too, but it seems that there are *way* more folks from the professional camp
> on comp.lang.python than otherwise. Do you have a gut feel for the % of
> hobbyists vs. professionals participating here?

Impossible to say. However, I would suggest that the more prolific
posters are going to be those who use Python more (and thus it's worth
investing more time in), which is going to skew the post stats towards
the professional end of the spectrum.

ChrisA