Python dictionaries are versatile, unordered collections of key-value pairs. They provide an efficient way to store and retrieve data using unique keys.

Creating Dictionaries

To create a dictionary, use curly braces {} or the dict() constructor. Keys and values are separated by colons, while pairs are separated by commas.


# Using curly braces
my_dict = {"name": "Alice", "age": 30, "city": "New York"}

# Using dict() constructor
another_dict = dict(name="Bob", age=25, city="London")

Accessing and Modifying Dictionary Elements

Access dictionary values using their corresponding keys. You can also modify existing values or add new key-value pairs.


# Accessing values
print(my_dict["name"])  # Output: Alice

# Modifying values
my_dict["age"] = 31

# Adding new key-value pairs
my_dict["occupation"] = "Engineer"

Dictionary Methods

Python provides several built-in methods for working with dictionaries:

get(): Safely retrieve values
keys(): Return all keys
values(): Return all values
items(): Return key-value pairs as tuples
pop(): Remove and return a value

Dictionary Comprehension

Create dictionaries efficiently using dictionary comprehension, similar to Python List Comprehension.


squares = {x: x**2 for x in range(5)}
# Result: {0: 0, 1: 1, 2: 4, 3: 9, 4: 16}

Common Use Cases

Dictionaries are ideal for:

Storing configuration settings
Caching function results
Counting occurrences of items
Implementing simple databases

Best Practices

When working with dictionaries, keep these tips in mind:

Use meaningful keys for better readability
Avoid mutable objects as keys
Use the in operator to check for key existence
Consider using defaultdict for handling missing keys

Related Concepts

To deepen your understanding of Python data structures, explore these related topics:

Mastering dictionaries is crucial for efficient data manipulation in Python. They offer a powerful way to organize and access information, making them indispensable in many programming scenarios.