#http://stackoverflow.com/questions/952914/making-a-flat-list-out-of-list-of-lists-in-python # for len(alist) = 1600 # A took 14.323 ms # B took 13.437 ms # C took 1.135 ms # where: # A = reduce(lambda x,y: x+y,l) # B = sum(l, []) # C = [item for sublist in l for item in sublist] def flat_list (mylist): a=sum(mylist,[]) return a #return sum doesn't work def flat_list_2(mylist): b=reduce(lambda x,y:x+y,mylist) return (b) def flat_list_3(mylist): c=[item for sublist in mylist for item in sublist] return c mylist1 = [[1, 1, 1, 1], [2, 3, 4, 5], [10, 20, 30]] #2D list print (flat_list(mylist1)) print (flat_list_2(mylist1)) print (flat_list_3(mylist1)) mylist2 = [[[0, 0, 0], [10, 10, 10], [20, 20, 20]], #3D list [[30, 30, 30], [40, 40, 40], [50, 50, 50]], [[10, 30, 40], [50, 60, 70], [80, 90, 100]]] print (flat_list(mylist2)) print (flat_list_2(mylist2)) print (flat_list_3(mylist2)) print (flat_list(flat_list(mylist2))) print (flat_list_2(flat_list(mylist2))) print (flat_list_3(flat_list(mylist2)))