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Add List Items

Adding items to a list is one of the most common operations in Python. Because lists are mutable, you can insert new elements at any position—beginning, middle, or end.
This topic covers all valid ways to add items to a list, with clear examples and edge cases.

Add Items Using append()

The append() method adds one item to the end of the list.
python
fruits = ["apple", "banana"]
fruits.append("cherry")
print(fruits)
python
numbers = [1, 2, 3]
numbers.append(4)
print(numbers)

Add Items Using insert()

The insert() method adds an item at a specific index.

Syntax

python
list.insert(index, value)
python
fruits = ["apple", "cherry"]
fruits.insert(1, "banana")
print(fruits)
python
numbers = [1, 2, 4]
numbers.insert(2, 3)
print(numbers)

Add Multiple Items Using extend()

The extend() method adds multiple items from another iterable.
python
numbers = [1, 2, 3]
numbers.extend([4, 5, 6])
print(numbers)
python
fruits = ["apple"]
fruits.extend(("banana", "cherry"))
print(fruits)

Add List to Another List (Important Difference)

Using append()

python
a = [1, 2]
b = [3, 4]
a.append(b)
print(a)
Result is a nested list.

Using extend()

python
a = [1, 2]
b = [3, 4]
a.extend(b)
print(a)
Result is a single flat list.

Add Items Using List Concatenation (+)

python
list1 = [1, 2]
list2 = [3, 4]

result = list1 + list2
print(result)
Original lists remain unchanged.

Add Items Using Slice Assignment

python
numbers = [1, 2, 5]
numbers[2:2] = [3, 4]
print(numbers)
python
numbers[:0] = [0]
print(numbers)

Add Items in a Loop

python
numbers = []

for i in range(5):
    numbers.append(i)

print(numbers)
python
items = []
for value in [10, 20, 30]:
    items.insert(0, value)

print(items)

Add Items Conditionally

python
numbers = [10, 20, 30]

if 40 not in numbers:
    numbers.append(40)

print(numbers)

Add Nested Items

python
matrix = [[1, 2], [3, 4]]
matrix.append([5, 6])
print(matrix)
python
matrix[0].append(10)
print(matrix)

Common Mistakes

Expecting append() to Add Multiple Items

python
numbers = [1, 2]
numbers.append([3, 4])
print(numbers)
This adds a list inside a list.

Using Wrong Index in insert()

python
numbers = [1, 2, 3]
numbers.insert(100, 4)
print(numbers)
Python inserts at the end, not an error.

Performance Tip

  • append() is fast and preferred
  • insert() at the beginning is slower for large lists
  • extend() is best for adding many items

Summary

  • append() adds one item at the end
  • insert() adds item at a specific index
  • extend() adds multiple items
  • + creates a new list
  • Slice assignment allows flexible insertion
  • Lists can be nested
  • Choose method based on use case
This topic naturally leads to:
  • Remove List Items
  • List Copying
  • List Comprehensions
  • List Performance Tips