How do I concatenate two lists in Python?

Question

How do I concatenate two lists in Python?

Example:

listone = [1, 2, 3]
listtwo = [4, 5, 6]

Expected outcome:

>&g         


        

Answer 1

It's worth noting that the itertools.chain function accepts variable number of arguments:

>>> l1 = ['a']; l2 = ['b', 'c']; l3 = ['d', 'e', 'f']
>>> [i for i in itertools.chain(l1, l2)]
['a', 'b', 'c']
>>> [i for i in itertools.chain(l1, l2, l3)]
['a', 'b', 'c', 'd', 'e', 'f']

If an iterable (tuple, list, generator, etc.) is the input, the from_iterable class method may be used:

>>> il = [['a'], ['b', 'c'], ['d', 'e', 'f']]
>>> [i for i in itertools.chain.from_iterable(il)]
['a', 'b', 'c', 'd', 'e', 'f']