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

[Mark H Harris]

On 4/4/14 10:42 PM, Rustom Mody wrote:
>
> Computer-hobbyists and computer-professionals are quite different sets of people.
>
    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?

> Are you aware
> That [people?] FORTRAN, COBOL, mainframes are still in use?

     Well, the S390 is still in use (running gnu/linux these days) and 
the z series machines from IBM. FORTRAN and COBOL have government 
(military) niche. I remember during the Y2K problem COBOL coders were 
working their butts off.  There is a 2014 standard doc replacing the 
2002 standard, believe.
     The last time I used FORTRAN IV was in about 1977, on the 
System360-44, but GNU still supports it, and as far as I know it still 
has a wide user group (mostly academic). I have it on my system here, 
but I don't use it.

> 1. Python is a fun language; its also a serious language

    A very serious language;  yes, its fun too.

> 2. Python is not as old as FORTRAN and COBOL but at 20 years its not exactly young either

    It won't have its day until it becomes ubiquitous... and its coming! 
  As the gnu/linux numbers continue to climb, more everyday is C python 
becoming ubiquitous. I'm hoping the ubiquitous version is C python 3.4+

> 3. Its reached far because core-devs behave responsibly
> towards different constituencies

    I think its because the language is flexible, extensible, &powerful 
(batteries included), and is supported by a world-wide community of 
software engineers (both amateur and professional) who are committed to 
its development and adoption world-wide. The PEP process has had a lot 
to due with this (and not to ape the BDFL) it has had a lot to due with 
some Dutch genius.    ;-)
    However, knowing your user-base is certainly important. Its always a 
problem (any venue, any environment) to try to please everyone. Tough 
choices have to be made. The C python community does a pretty good job 
of this. Python-ideas and the PEP process are a unique and unparalleled 
strategy for enhancement. Very nice.
    Having said that, I do believe that the migration to C python3 has 
been too conservative. Nobody wants to maintain a fork, not really. I 
don't think its something anyone should be afraid of. Somebody should 
put a date on C python 3.4+ migration and cut off support for 2.7.x/ 
Its just an opinion. If 'Twisted' isn't ready for 3.x, well, they need 
to get ready. That's also just an opinion.


marcus