9.1. A list is a sequence

Like a string, a list is a sequence of values. In a string, the values are characters; in a list, they can be any type. The values in list are called elements or sometimes items.

There are several ways to create a new list; the simplest is to enclose the elements in square brackets (“[” and “]”):

[10, 20, 30, 40]
['crunchy frog', 'ram bladder', 'lark vomit']

The first example is a list of four integers. The second is a list of three strings. The elements of a list don’t have to be the same type. The following list contains a string, a float, an integer, and (lo!) another list:

['spam', 2.0, 5, [10, 20]]

A list within another list is nested.

A list that contains no elements is called an empty list; you can create one with empty brackets, [].

As you might expect, you can assign list values to variables:

cheeses = ['Cheddar', 'Edam', 'Gouda'] numbers = [17, 123] empty = [] print(cheeses, numbers, empty)

Q-2: True or False? A list can contain only integer items.

• True
• lists can have different data types.
• False
• lists can contain any combination of items, even other lists!

Q-3: What is the length of the list [“Sue”,”Maria”,5,”Erica”]?

• 1
• There is only one number in the list, but that is not the length.
• 3
• There are three strings in the list, but that is not the length.
• 4
• There are 4 items in this list (three strings and a number) making the length 4.
• 5
• The value of the number in this list is 5, but that is not the length.

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