Practical Programming, 2nd Edition

Working with a List of Lists

We said in ​Lists Are Heterogeneous​, that lists can contain any type of data. That means that they can contain other lists. A list whose items are lists is called a nested list. For example, the following nested list describes life expectancies in different countries:

>>> life = [['Canada', 76.5], ['United States', 75.5], ['Mexico', 72.0]]

Here is the memory model that results from execution of that assignment statement:

Notice that each item in the outer list is itself a list of two items. We use the standard indexing notation to access the items in the outer list: ...