Learn Dictionaries in Python with real-life examples. Understand key-value pairs, dictionary methods, loops, dictionary comprehension, and practical use cases in Python programming.
When working with Python, sometimes we need to store information in pairs.
For example:
- A student’s name and their marks
- A country and its capital
- A product and its price
For such cases, dictionaries are the best choice in Python!
What is a Dictionary in Python?
A dictionary is a collection of data stored in key-value pairs.
- The key is like a label (unique).
- The value is the data linked to that key.
👉 Syntax:
my_dict = {
"key1": "value1",
"key2": "value2"
}
Example:
student = {
"name": "Rahul",
"age": 20,
"marks": 85
}
print(student)Output:
{'name': 'Rahul', 'age': 20, 'marks': 85}
Creating a Dictionary
- Empty dictionary
data = {}- With values
car = {"brand": "Toyota", "model": "Fortuner", "year": 2022}- Using dict() constructor
info = dict(name="Amit", age=25, city="Delhi")Accessing Dictionary Values
You can access values using keys:
student = {"name": "Rahul", "marks": 85}
print(student["name"]) # Rahul
print(student["marks"]) # 85⚠️ If the key doesn’t exist, it throws an error.
To avoid this, use get():
print(student.get("age", "Not Found"))Read More: Sets in Python
Updating and Adding Items
student = {"name": "Rahul", "marks": 85}
# Update
student["marks"] = 90
# Add new key-value pair
student["age"] = 20
print(student)Output:
{'name': 'Rahul', 'marks': 90, 'age': 20}
Removing Items
- pop(key) → Removes item with the given key.
student.pop("marks")- popitem() → Removes the last inserted item.
student.popitem()- del → Deletes key or entire dictionary.
del student["name"] # Deletes 'name' key
del student # Deletes entire dictionary- clear() → Removes all items.
student.clear()Useful Dictionary Methods
| Method | Description | Example |
|---|---|---|
keys() | Returns all keys | student.keys() |
values() | Returns all values | student.values() |
items() | Returns key-value pairs | student.items() |
update() | Updates dictionary with another dict | student.update({"age": 22}) |
copy() | Returns a shallow copy | student.copy() |
Looping Through a Dictionary
student = {"name": "Rahul", "marks": 90, "age": 20}
for key, value in student.items():
print(key, ":", value)Output:
name : Rahul
marks : 90
age : 20
Real-Life Examples of Dictionaries
Example 1: Country-Capital Dictionary
capitals = {
"India": "New Delhi",
"France": "Paris",
"Japan": "Tokyo"
}
print("Capital of Japan is:", capitals["Japan"])
# Output: Capital of Japan is: TokyoExample 2: Student Marks Record
marks = {
"Amit": 85,
"Rahul": 90,
"Neha": 78
}
print("Rahul's Marks:", marks["Rahul"])
# Output: Rahul's Marks: 90Example 3: Shopping Cart System
cart = {
"Laptop": 55000,
"Mobile": 20000,
"Headphones": 1500
}
total = sum(cart.values())
print("Total Price:", total)
# Output: Total Price: 76500Dictionary Comprehension
Just like list comprehension, we can create dictionaries in one line.
squares = {x: x**2 for x in range(1, 6)}
print(squares)Output:
{1: 1, 2: 4, 3: 9, 4: 16, 5: 25}
Final Thoughts
Dictionaries are one of the most powerful data structures in Python.
They are perfect when you want to map information like a real-world dictionary (word → meaning).
In this post, you learned:
- What dictionaries are
- How to create, access, update, and delete
- Useful methods and loops
- Real-life examples
- Dictionary comprehension
Mastering dictionaries will make your coding more efficient and help you build real-world projects like student management systems, shopping carts, and APIs.
FAQs – Dictionaries in Python
How is a dictionary different from a list?
A list stores data in an ordered sequence (index-based), while a dictionary stores data as key-value pairs (not based on indexes).
Can dictionary keys be duplicate?
No. Keys in a dictionary must be unique. If you add a duplicate key, the latest value will overwrite the previous one.
Can dictionary keys be of any data type?
No. Keys must be immutable types like strings, numbers, or tuples. Lists or other dictionaries cannot be used as keys.
How can I loop through a dictionary?
You can use for key, value in dict.items() to loop through both keys and values.
What’s Next?
In the next post, we’ll learn about the Student Management System in Python