List are Mutable

Unlike string lists are mutable. 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 bracket specify the index. Remember that the indices start at 0:

>>> print guitars[0]
Gibson

As mentioned before lists are mutable and that means that 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.

>>> guitars = ['Gibson', 'Fender', 'Jackson']
>>> guitars[0] = 'Epiphone'
>>> print guitars
['Epiphone', 'Fender', 'Jackson']

So we’ve changed the 0-th element of guitars, form ‘Gibson’ to ‘Epiphone’.

Think of a list as a relationship between indices and elements. This relationship is called mapping; each index ‘maps to’ one of the elements.

List indices work the same way as string indices:

Any integer can be used as index

If you try to read or write an element that doesn’t exist, you’ll get IndexError.

If an index has a negative value, it counts backward from the end of the list.

The in operator also works on lists.

>>> guitars = ['Gibson', 'Fender', 'Jackson']
>>> 'Gibson' in guitars
True
>>> 'Fender' in guitars
True