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Section 10.3 List 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.

Check your understanding

Checkpoint 10.3.1.

    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.

Checkpoint 10.3.2.

    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.
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