5.1 More on Lists

The list data type has some more methods. Here are all of the methods of list objects:

insert(i, x)

Insert an item at a given position. The first argument is the index of the element before which to insert, so a.insert(0, x) inserts at the front of the list, and a.insert(len(a), x) is equivalent to a.append(x).

append(x)

Equivalent to a.insert(len(a), x).

index(x)

Return the index in the list of the first item whose value is x. It is an error if there is no such item.

remove(x)

Remove the first item from the list whose value is x. It is an error if there is no such item.

sort()

Sort the items of the list, in place.

reverse()

Reverse the elements of the list, in place.

count(x)

Return the number of times x appears in the list.

An example that uses all list methods:

>>> a = [66.6, 333, 333, 1, 1234.5]
>>> print a.count(333), a.count(66.6), a.count('x')
2 1 0
>>> a.insert(2, -1)
>>> a.append(333)
>>> a
[66.6, 333, -1, 333, 1, 1234.5, 333]
>>> a.index(333)
1
>>> a.remove(333)
>>> a
[66.6, -1, 333, 1, 1234.5, 333]
>>> a.reverse()
>>> a
[333, 1234.5, 1, 333, -1, 66.6]
>>> a.sort()
>>> a
[-1, 1, 66.6, 333, 333, 1234.5]