# import the itertools
import itertools

# Declaring the list geek
n_lst = [[1, 2], [3, 4], [5, 6]]

# chain.from_iterable() function returns the elements of nested list
# and iterate from first list of iterable till the last
# end of the list

lst = list(itertools.chain.from_iterable(n_lst))
print(lst) # [1, 2, 3, 4, 5, 6]

print [y for x in n_lst for y in x] # [1, 2, 3, 4, 5, 6]