liuerfire Wang wrote: > Here is a list x = [b, a, c] (a, b, c are elements of x. Each of them are > different type). Now I wanna generate a new list as [b, b, a, a, c, c]. > > I know we can do like that: > > tmp = [] > for i in x: > tmp.append(i) > tmp.append(i) > > However, I wander is there a more beautiful way to do it, like [i for i in > x]?
Using itertools: >>> items [b, a, c] >>> from itertools import chain, tee, repeat >>> list(chain.from_iterable(zip(*tee(items)))) [b, b, a, a, c, c] Also using itertools: >>> list(chain.from_iterable(repeat(item, 2) for item in items)) [b, b, a, a, c, c] For lists only, should be fast: >>> result = 2*len(items)*[None] >>> result[::2] = result[1::2] = items >>> result [b, b, a, a, c, c] But I would call none of these beautiful... -- http://mail.python.org/mailman/listinfo/python-list
