Do you mean append?
>>> x = [1,2,3]
>>> y = [4,5,6]
>>> x.append(y)
>>> x
[1, 2, 3, [4, 5, 6]]
Or merge?
>>> x = [1,2,3]
>>> y = [4,5,6]
>>> x + y
[1, 2, 3, 4, 5, 6]
>>> x.extend(y)
>>> x
[1, 2, 3, 4, 5, 6]
foo = [1, 2, 3]
bar = [4, 5, 6]
foo.append(bar) --> [1, 2, 3, [4, 5, 6]]
foo.extend(bar) --> [1, 2, 3, 4, 5, 6]
If you want to add the elements in a list (list2) to the end of other list (list), then you can use the list extend method
list = [1, 2, 3]
list2 = [4, 5, 6]
list.extend(list2)
print list
[1, 2, 3, 4, 5, 6]
Or if you want to concatenate two list then you can use + sign
list3 = list + list2
print list3
[1, 2, 3, 4, 5, 6]
If we just do x.append(y), y gets referenced into x such that any changes made to y will affect appended x as well. So if we need to insert only elements, we should do following:
x = [1,2,3]
y = [4,5,6]
x.append(y[:])
The question does not make clear what exactly you want to achieve.
List has the append method, which appends its argument to the list:
>>> list_one = [1,2,3]
>>> list_two = [4,5,6]
>>> list_one.append(list_two)
>>> list_one
[1, 2, 3, [4, 5, 6]]
There's also the extend method, which appends items from the list you pass as an argument:
>>> list_one = [1,2,3]
>>> list_two = [4,5,6]
>>> list_one.extend(list_two)
>>> list_one
[1, 2, 3, 4, 5, 6]
And of course, there's the insert method which acts similarly to append but allows you to specify the insertion point:
>>> list_one.insert(2, list_two)
>>> list_one
[1, 2, [4, 5, 6], 3, 4, 5, 6]
To extend a list at a specific insertion point you can use list slicing (thanks, @florisla):
>>> l = [1, 2, 3, 4, 5]
>>> l[2:2] = ['a', 'b', 'c']
>>> l
[1, 2, 'a', 'b', 'c', 3, 4, 5]
List slicing is quite flexible as it allows to replace a range of entries in a list with a range of entries from another list:
>>> l = [1, 2, 3, 4, 5]
>>> l[2:4] = ['a', 'b', 'c'][1:3]
>>> l
[1, 2, 'b', 'c', 5]
You can also just do...
x += y
Source: Stackoverflow.com