How to remove the innermost level of nesting in a list of lists of varying lengths

Question

I\'m trying to remove the innermost nesting in a list of lists of single element length lists. Do you know a relatively easy way (converting to NumPy arrays is fine) to get

Answer 1

>>> from operator import add
>>> lists = [ [ [1],[2],[3],[4], [5] ],   [ [6],[7],[8] ] , [ [11],[12] ] ]
>>> [reduce(add, lst) for lst in lists]
[[1, 2, 3, 4, 5], [6, 7, 8], [11, 12]]

This is not a very efficient, as it rebuilds a list each time add is called. Alternatively you can use sum or a simple list comprehension, as seen in the other answers.