Lists can contain other lists (sublists):
>>> birthdays = [("Marc","12/10/67"), ("Steve","3/4/91")]
>>>
>>> marc = birthdays[0]
>>> marc
('Marc', '12/10/67')
>>>
>>> print("Marc's birthday: " + birthdays[0][1])
Marc's birthday: 12/10/67
What about the following list?
>>> x = [42]
>>> x.append(x)
Attention:
>>> a = [3,5]
>>> x = []
>>> y =[]
>>> x.append(a)
>>> y.append(a)
>>> y
[[3, 5]]
>>> x
[[3, 5]]
>>> a.append(42)
>>> x
[[3, 5, 42]]
>>> y
[[3, 5, 42]]