A list is an ordered, mutable collection of items in Python. Lists allow storing multiple values in a single variable and provide powerful methods for manipulation.
1. Creating Lists
Lists are created using square brackets [] and can contain different data types.
Example:
fruits = ["apple", "banana", "cherry"]
numbers = [1, 2, 3, 4, 5]
mixed = ["Python", 3.14, True]
print(fruits, numbers, mixed)
Output:
['apple', 'banana', 'cherry'] [1, 2, 3, 4, 5] ['Python', 3.14, True]
2. Accessing List Elements
List elements are indexed, starting from 0.
Example:
fruits = ["apple", "banana", "cherry"]
print(fruits[0]) # First item
print(fruits[-1]) # Last item
Output:
apple
cherry
3. Slicing Lists
Retrieve a part of a list using slicing.
Example:
numbers = [10, 20, 30, 40, 50]
print(numbers[1:4]) # Elements from index 1 to 3
print(numbers[:3]) # First 3 elements
print(numbers[::-1]) # Reverse the list
4. Modifying Lists
Lists are mutable, meaning their elements can be changed.
Example:
fruits = ["apple", "banana", "cherry"]
fruits[1] = "orange"
print(fruits) # Output: ['apple', 'orange', 'cherry']
5. Adding and Removing Elements
Adding Elements
fruits = ["apple", "banana"]
fruits.append("cherry") # Add at end
fruits.insert(1, "orange") # Insert at index 1
print(fruits)
Removing Elements
fruits.remove("banana") # Remove by value
popped = fruits.pop() # Remove last item
print(fruits, popped)
6. Looping Through a List
Example:
fruits = ["apple", "banana", "cherry"]
for fruit in fruits:
print(fruit)
7. List Comprehensions
List comprehensions provide a concise way to create lists.
Example:
squares = [x ** 2 for x in range(1, 6)]
print(squares) # Output: [1, 4, 9, 16, 25]
8. Sorting and Reversing Lists
Example:
numbers = [5, 2, 9, 1, 5, 6]
numbers.sort() # Sort ascending
print(numbers)
numbers.reverse() # Reverse order
print(numbers)
9. Checking Membership
Example:
fruits = ["apple", "banana", "cherry"]
print("banana" in fruits) # Output: True
print("grape" not in fruits) # Output: True
10. Copying Lists
Avoid modifying the original list unintentionally.
Example:
original = [1, 2, 3]
copy1 = original.copy()
copy2 = list(original)
copy3 = original[:]
print(copy1, copy2, copy3)
11. List Methods Summary
| Method | Description |
|---|---|
append(x) | Adds x to the end of the list |
insert(i, x) | Inserts x at index i |
remove(x) | Removes first occurrence of x |
pop(i) | Removes and returns element at index i (default: last) |
sort() | Sorts list in ascending order |
reverse() | Reverses the order of elements |
copy() | Creates a shallow copy of the list |
12. Summary
✅ Lists store multiple values in a single variable.
✅ Lists are mutable, meaning they can be modified.
✅ List operations include indexing, slicing, adding, removing, sorting, and looping.
✅ List comprehensions provide a concise way to generate lists.