Lists, Tuple, Dictionary and Sets

Python provides several built-in data structures that help organize, store, and manipulate data efficiently. These are Lists, Tuples, Dictionaries, and Sets.

Lists

A list is an ordered, mutable (changeable) collection of elements. It allows duplicate values and can store different data types.

• Ordered (maintains insertion order)
• Mutable (can be modified)
• Allows duplicates
• Can store mixed data types

# Creating a list
my_list = [10, 20, 30, 40, 50]

# Accessing elements
print(my_list[0])   # First element
print(my_list[-1])  # Last element

# Modifying elements
my_list[1] = 25

# Adding elements
my_list.append(60)

# Removing elements
my_list.remove(30)

print(my_list)

10
50
[10, 25, 40, 50, 60]

List Operations

numbers = [1, 2, 3]

numbers.append(4)       # Add at end
numbers.insert(1, 10)   # Insert at index
numbers.pop()           # Remove last
numbers.sort()          # Sort list

print(numbers)

[1, 2, 3, 10]

Tuples

A tuple is an ordered, immutable collection of elements. Once created, it cannot be changed.

• Ordered
• Immutable (cannot modify)
• Allows duplicates
• Faster than lists (in many cases)

# Creating a tuple
my_tuple = (10, 20, 30, 40)

# Accessing elements
print(my_tuple[0])
print(my_tuple[-1])

# Tuple with mixed data types
mixed_tuple = (1, "Hello", 3.5)

print(mixed_tuple)

10
40
(1, 'Hello', 3.5)

Immutability

my_tuple = (1, 2, 3)

# This will cause an error
# my_tuple[0] = 10

TypeError: 'tuple' object does not support item assignment

Dictionaries

A dictionary stores data in key-value pairs. It is unordered (before Python 3.7), but now maintains insertion order.

• Key-value structure
• Keys must be unique
• Mutable
• Fast lookup using keys

# Creating a dictionary
student = {
    "name": "Rahul",
    "age": 21,
    "course": "BCA"
}

# Accessing values
print(student["name"])

# Adding new key-value pair
student["marks"] = 85

# Updating value
student["age"] = 22

# Removing element
del student["course"]

print(student)

Rahul
{'name': 'Rahul', 'age': 22, 'marks': 85}

Dictionary Methods

data = {"a": 1, "b": 2}

print(data.keys())
print(data.values())
print(data.items())

dict_keys(['a', 'b'])
dict_values([1, 2])
dict_items([('a', 1), ('b', 2)])

Sets

A set is an unordered collection of unique elements. It does not allow duplicates.

• Mutable
• Useful for mathematical operations

# Creating a set
my_set = {1, 2, 3, 4}

# Adding elements
my_set.add(5)

# Removing elements
my_set.remove(2)

print(my_set)

{1, 3, 4, 5}

Set Operations

A = {1, 2, 3}
B = {3, 4, 5}

print(A.union(B))        # Union
print(A.intersection(B)) # Intersection
print(A.difference(B))   # Difference

{1, 2, 3, 4, 5}
{3}
{1, 2}

Write a program to remove duplicates from a list

numbers = [1, 2, 2, 3, 4, 4, 5]
unique_numbers = list(set(numbers))
print(unique_numbers)

[1, 2, 3, 4, 5]