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

[Roy Smith]

In article <87txahi68z.fsf at elektro.pacujo.net>,
 Marko Rauhamaa <marko at pacujo.net> wrote:

> (But no, I wouldn't name my variables in Hebrew because the next
> maintainer might not have a keyboard like mine.)

Have you ever done any work in PHP?  Many of the error messages are 
Hebrew, transliterated into English.  I've gotten many a 
T_PAAMAYIM_NEKUDOTAYIM error.