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

[Mark H Harris]

On 3/30/14 10:22 AM, Steven D'Aprano wrote:
> In 1991, there was no wireless, no mobile computing, hardly any public
> Internet outside of the universities. It was before the Eternal
> September, and only a few years after the Great Renaming.

    I was using arpanet since the late 1970s.

> Python had just
> been released for the first time, and Windows 3.1 hadn't been (although
> 3.0 had). There was no Netscape, no Mosaic graphical web browsers. Steve
> Jobs hadn't returned to Apple yet, Apple was still losing money and mind-
> share, and Google didn't even exist. It was a different era.

    Command line all the way babe... uuencode uudecode base64  whoohoo.

    ftp, and all the rest...


> 1991 is 23 years ago. In "computer years", I consider that almost eight
> generations, about the same as 160 years in human terms.

    Bologna, Oscar Meyer Bologna, USDA Prime.  That's just plain silly. 
Yes, a lot of things have happened since 1991, but 1991 was yesterday; 
and in the big scheme of things, not much really has happened (oh, yeah, 
smaller and faster; Moores law moves forward, so what?)  We're still 
using von Nuemann processors, we're still using all the same stupid 
programming tricks; the only thing that has changed is that computers 
use a fraction of the power they did, they are very tiny, and they are 
very fast. so what?  We have unicode!  yeahhhh. ASCII is dead. Microsoft 
is dying. Gun/Linux rules. I still program in BASIC at least once a 
week, and we all still have trouble communicating around the globe.

>> I didn't really start using unicode
>> until about 5 years ago; python has only really used it since python3.
>> right?
>
> No. Python 2.2 introduced Unicode.

I didn't ask when it was introduced, I asked when it became useful? 
Python was experimenting with unicode in version 2.  It became more 
fully useful in version 3. I didn't use it in version 2--- way too 
frustrating.

Unicode in python3.x is (mostly) working correctly. Congratulations to 
all who worked on it, hat is off.  The problem with unicode is that it 
is just a specification. The consortium cannot force or code anything. 
They control the scripts and make the specifications. It is left to 
*everyone* else to implement. And not everyone is taking on that task 
with the same gusto, if you follow my meaning.


marcus