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

[Mark H Harris]

On 3/22/14 3:59 PM, vasudevram wrote:
>
> Thanks to all those who answered.
>
> - Vasudev

I am wondering if the question was answered?


>>>>
>>>> x = [[1,2],[3,4],[5,6]]
>>>> import ast
>>>> ast.dump(ast.parse('[x for x in x for x in x]'))
 >
> "Module(body=
 >
> [Expr(value=ListComp(elt=Name(id='x', ctx=Load()),
 >
> generators=
 >
> [comprehension(target=Name(id='x', ctx=Store()), iter=Name(id='x', ctx=Load()), ifs=[]),
 >
> comprehension(target=Name(id='x', ctx=Store()), iter=Name(id='x', ctx=Load()), ifs=[])]))])"
>>>>

This is really, I think, the answer to the OPs question. Knowing how 
python is parsing the comprehension of comprehensions is important, yes?

Obviously each x is within a different scope, within a separate 
iterator. This seems to unwind from right to left?

I didn't see any ast entries in the thread, so just wondering.

marcus