Extend vs Append

Could be useful.

>>> x = [1,2,3]

>>> y = [4,5,6]

>>> x.append(y)

>>> x

[1, 2, 3, [4, 5, 6]]

>>> x.remove(y)

>>> x

[1, 2, 3]

>>> x.extend(y)

>>> x

[1, 2, 3, 4, 5, 6]

>>>