A method is a function that belongs to a value. You call it with a dot: mylist.append(x). Lists come with a set of methods for changing their contents.

Adding items

fruits = ["apple", "banana"]

fruits.append("cherry")
print(fruits)

fruits.insert(0, "avocado")
print(fruits)

append() adds to the end — by far the most common. insert(index, item) puts an item at a specific position and shifts everything after it along.

fruits = ["apple"]
fruits.extend(["banana", "cherry"])
print(fruits)

extend() adds every item from another list. Note the difference: append(["b", "c"]) would add one item that happens to be a list, giving you a nested list instead.

Removing items

fruits = ["apple", "banana", "cherry"]

fruits.remove("banana")
print(fruits)

last = fruits.pop()
print(last)
print(fruits)

remove(value) deletes the first matching item by value. pop() removes and returns the last item — useful when you want the value as you take it. pop(0) removes the first instead.

del fruits[0] and fruits.clear() also work, for deleting by index and emptying the list.

Sorting and reversing

numbers = [3, 1, 4, 1, 5]

numbers.sort()
print(numbers)

numbers.reverse()
print(numbers)

sort() changes the list in place and returns None. That last part catches people out:

numbers = [3, 1, 2]
result = numbers.sort()
print(result)

That prints None, not a sorted list. If you want a sorted copy while leaving the original alone, use the sorted() function instead:

numbers = [3, 1, 2]
print(sorted(numbers))
print(numbers)

Searching

fruits = ["apple", "banana", "cherry"]

print("banana" in fruits)
print(fruits.index("cherry"))
print(fruits.count("apple"))

in gives a boolean, index() gives the position, and count() gives how many times a value appears.

Try it yourself

Start with [3, 1, 2]. Append 4, sort it, then print the list and its length.

Checkpoint

• append() adds one item; extend() adds many; insert() adds at a position.
• remove() deletes by value; pop() deletes by position and returns the item.
• sort() sorts in place and returns None; sorted() returns a new sorted list.
• in, index(), and count() search a list.