Possible Duplicate:
Making a flat list out of list of lists in Python
how can I create form a list e.g [[1,2],[3,4]] or [(1,2),(3,4)] the list [1,2,3,4]
list comprehension(or map, filter)doesn't seems to have map object to more than one other object.
like SelectMany in C#'s LINQ
Standard libs are cool:
>>> import itertools
>>> l = [[1,2],[3,4]]
>>> list(itertools.chain(*l))
[1, 2, 3, 4]
Provided you know that it will be exactly 2 levels deep, you can do
[j for i in [[1,2],[3,4]] for j in i]
where you iterate with i over the list, giving i successively the values [1,2] and [3,4], and with j over these sub-lists. Thus this expression results to [1, 2, 3, 4].
>>l=[1,2,3,4]
>>zip(l[:2:],l[1:][:2:])
[(1, 2), (2, 3)]
>>l=[(1, 2), (2, 3)]
>>sum(l,())
(1, 2, 2, 3)
It's not just what you need?
