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

[Marko Rauhamaa]

Steven D'Aprano <steve+comp.lang.python at pearwood.info>:

> On Sun, 06 Apr 2014 12:05:16 +0300, Marko Rauhamaa wrote:
>> Python, BTW, is perfectly suitable for computer science. 
>
> I don't think it is. Python is not a pure functional language, so it's 
> very difficult to prove anything about the code apart from running it. 

Many classic CS ideas are expressed in terms of an Algol-like language.
Nothing would prevent you from framing those ideas in a Python-like
(pseudo)language. The question is mostly whether you prefer begin/end,
braces or indentation.

>>  * combinatory birds in forests
>
> I don't believe that came from academia. If I've understood correctly, 
> that was from a non-academic book on applying the lambda calculus to 
> solve practical applications.

It is academic because the author, Raymond Smullyan, was a professor of
philosophy and, more importantly, my professor selected that as a
textbook for us graduate students.


Marko