In this section, we will explore two fundamental data structures in programming: dictionaries and sets. These structures are essential for efficient data management and manipulation. We will cover their definitions, uses, and practical examples to help you understand how to implement them in your programs.
Dictionaries
What is a Dictionary?
A dictionary is a collection of key-value pairs where each key is unique. It is also known as a hash map or associative array in other programming languages. Dictionaries are used to store data values like a map, which, unlike a list or array, allows you to quickly retrieve, add, or modify data based on a unique key.
Key Concepts
- Keys: Unique identifiers used to access values.
- Values: Data associated with keys.
- Key-Value Pair: A combination of a key and its corresponding value.
Example in Python
# Creating a dictionary
student_grades = {
"Alice": 85,
"Bob": 92,
"Charlie": 78
}
# Accessing a value
print(student_grades["Alice"]) # Output: 85
# Adding a new key-value pair
student_grades["David"] = 88
# Modifying an existing value
student_grades["Alice"] = 90
# Deleting a key-value pair
del student_grades["Charlie"]
# Iterating through a dictionary
for student, grade in student_grades.items():
print(f"{student}: {grade}")Common Operations
| Operation | Syntax | Description |
|---|---|---|
| Access Value | dict[key] |
Retrieves the value associated with key. |
| Add/Modify Value | dict[key] = value |
Adds or updates the value for key. |
| Delete Key-Value | del dict[key] |
Removes the key-value pair for key. |
| Iterate | for key, value in dict.items(): |
Iterates through all key-value pairs. |
| Check Existence | key in dict |
Checks if key exists in the dictionary. |
Practical Exercise
Exercise 1:
Create a dictionary to store the names and ages of five people. Then, perform the following operations:
- Add a new person to the dictionary.
- Update the age of one person.
- Delete one person from the dictionary.
- Print all the names and ages.
Solution:
# Step 1: Create the dictionary
people_ages = {
"John": 25,
"Jane": 30,
"Mike": 22,
"Anna": 28,
"Tom": 35
}
# Step 2: Add a new person
people_ages["Lucy"] = 27
# Step 3: Update the age of one person
people_ages["John"] = 26
# Step 4: Delete one person
del people_ages["Tom"]
# Step 5: Print all names and ages
for name, age in people_ages.items():
print(f"{name}: {age}")Sets
What is a Set?
A set is an unordered collection of unique elements. Sets are used to store multiple items in a single variable, and they automatically remove duplicate values. They are particularly useful for membership testing and eliminating duplicate entries.
Key Concepts
- Unordered: Elements do not have a specific order.
- Unique Elements: No duplicate elements are allowed.
Example in Python
# Creating a set
fruits = {"apple", "banana", "cherry"}
# Adding an element
fruits.add("orange")
# Removing an element
fruits.remove("banana")
# Checking membership
print("apple" in fruits) # Output: True
# Iterating through a set
for fruit in fruits:
print(fruit)Common Operations
| Operation | Syntax | Description |
|---|---|---|
| Add Element | set.add(element) |
Adds element to the set. |
| Remove Element | set.remove(element) |
Removes element from the set. |
| Check Membership | element in set |
Checks if element is in the set. |
| Iterate | for element in set: |
Iterates through all elements in the set. |
Practical Exercise
Exercise 2:
Create a set to store the names of five different fruits. Then, perform the following operations:
- Add a new fruit to the set.
- Remove one fruit from the set.
- Check if a specific fruit is in the set.
- Print all the fruits.
Solution:
# Step 1: Create the set
fruits = {"apple", "banana", "cherry", "mango", "grape"}
# Step 2: Add a new fruit
fruits.add("orange")
# Step 3: Remove one fruit
fruits.remove("banana")
# Step 4: Check if a specific fruit is in the set
print("apple" in fruits) # Output: True
# Step 5: Print all the fruits
for fruit in fruits:
print(fruit)Conclusion
In this section, we have learned about dictionaries and sets, two powerful data structures in programming. Dictionaries allow us to store and manipulate data using key-value pairs, while sets provide a way to handle collections of unique elements. Understanding these structures and their operations is crucial for efficient data management in your programs.
Next, we will move on to more advanced data structures and algorithms to further enhance your programming skills.