# How to Think Like a Computer Scientist: The PreTeXt Interactive Edition

## Section10.3List Length

As with strings, the function len returns the length of a list (the number of items in the list). However, since lists can have items which are themselves lists, it important to note that len only returns the top-most length. In other words, sublists are considered to be a single item when counting the length of the list.

### Checkpoint10.3.1.

What is printed by the following statements?
alist = [3, 67, "cat", 3.14, False]
print(len(alist))

• 4
• len returns the actual number of items in the list, not the maximum index value.
• 5
• Yes, there are 5 items in this list.

### Checkpoint10.3.2.

What is printed by the following statements?
alist = [3, 67, "cat", [56, 57, "dog"], [ ], 3.14, False]
print(len(alist))

• 7
• Yes, there are 7 items in this list even though two of them happen to also be lists.
• 8
• len returns the number of top level items in the list. It does not count items in sublists.