The syntax for accessing the elements of a list is the same as for accessing the characters of a string—the bracket operator. The expression inside the brackets specifies the index. Remember that the indices start at 0:
>>> print cheeses[0]Cheddar
Unlike strings, lists are mutable because you can change the order of items in a list or reassign an item in a list. When the bracket operator appears on the left side of an assignment, it identifies the element of the list that will be assigned.
>>> numbers = [17, 123]>>> numbers[1] = 5>>> print numbers[17, 5]
The one-eth element of numbers, which used to be 123, is now 5.
You can think of a list as a relationship between indices and elements. This relationship is called a mapping; each index “maps to” one of the elements.
List indices work the same way as string indices:
- Any integer expression can be used as an index.
- If you try to read or write an element that does not exist, you get an IndexError.
- If an index has a negative value, it counts backward from the end of the list.
The in operator also works on lists.
>>> cheeses = ['Cheddar', 'Edam', 'Gouda']>>> 'Edam' in cheesesTrue>>> 'Brie' in cheesesFalse
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