List Methods

Essential List Methods: Adding and Removing Elements

Let’s start with the methods that modify the list itself:

append(item): Adds an item to the end of the list.

my_list = [1, 2, 3]
my_list.append(4)
print(my_list)  # Output: [1, 2, 3, 4]

insert(index, item): Inserts an item at a specific index.

my_list.insert(1, 5)
print(my_list)  # Output: [1, 5, 2, 3, 4]

extend(iterable): Adds all items from an iterable (like another list or tuple) to the end of the list.

my_list.extend([6, 7])
print(my_list)  # Output: [1, 5, 2, 3, 4, 6, 7]

remove(item): Removes the first occurrence of a specific item. Raises a ValueError if the item is not found.

my_list.remove(2)
print(my_list)  # Output: [1, 5, 3, 4, 6, 7]

pop([index]): Removes and returns the item at the specified index (defaults to the last item). Raises an IndexError if the index is out of range.

removed_item = my_list.pop(0)
print(removed_item)  # Output: 1
print(my_list)  # Output: [5, 3, 4, 6, 7]

clear(): Removes all items from the list.

my_list.clear()
print(my_list)  # Output: []

List Methods for Searching and Manipulation

These methods help you find and rearrange elements within your list:

index(item): Returns the index of the first occurrence of an item. Raises a ValueError if the item is not found.

my_list = [1, 2, 3, 2, 4]
index_of_2 = my_list.index(2)
print(index_of_2)  # Output: 1

count(item): Returns the number of times an item appears in the list.

count_of_2 = my_list.count(2)
print(count_of_2)  # Output: 2

sort(): Sorts the list in ascending order (in-place). For custom sorting, use the key argument.

my_list.sort()
print(my_list)  # Output: [1, 2, 2, 3, 4]

reverse(): Reverses the order of items in the list (in-place).

my_list.reverse()
print(my_list)  # Output: [4, 3, 2, 2, 1]

copy(): Creates a shallow copy of the list. Important for avoiding unintended modifications to the original list.

my_list_copy = my_list.copy()
my_list_copy.append(5)
print(my_list)      # Output: [4, 3, 2, 2, 1]
print(my_list_copy) # Output: [4, 3, 2, 2, 1, 5]

More Advanced List Operations

These methods provide further control and functionality:

list.copy(): Creates a shallow copy of the list.