List Comprehension Question: One to Many Mapping?

[Paul Rubin]

Boris Borcic <bborcic at gmail.com> writes:
> >> For example, if I have x=[ [1,2], [3,4] ]
> >>
> >> What I want is a new list of list that has four sub-lists:
> >>
> >> [[1,2], [f(1), f(2)], [3,4], [f(3), f(4)]]
> > [[a, map(f,a)] for a in x]
> 
> no, that one will be [[[1,2], [f(1), f(2)]], [[3,4], [f(3), f(4)]]]
> eg two sublists instead of four.

Oh ugh, I misread the original request and thought the extra brackets
were there.  I think the following works and is reasonably intuitive:

    from itertools import chain
    y = list(chain(*([a, map(f,a)] for a in x)))

But the original request itself seems a bit weird.