Dictionaries

Introduction to Python for Developers

George Boorman

Curriculum Manager, DataCamp

Products list

prices = [10, 20, 30, 15, 25, 35]


# Product IDs
product_ids = ["AG32", "HT91", "PL65", "OS31", "KB07", "TR48"]

Dictionary

Dictionary = key-value pairs

Dictionary annotated with the word (key) and definition (value)

¹ https://unsplash.com/@sandym10

Why use dictionaries?

user_id
order_number
date
value
payment_method

ip_address
location

Cash

Computer network

¹ https://unsplash.com/@sharonmccutcheon; https://unsplash.com/@jjying

Creating a dictionary

# Creating a dictionary
products_dict =

Creating a dictionary

# Creating a dictionary
products_dict = {

Creating a dictionary

# Creating a dictionary
products_dict = {"AG32"

Creating a dictionary

# Creating a dictionary
products_dict = {"AG32":

Creating a dictionary

# Creating a dictionary
products_dict = {"AG32": 10

Creating a dictionary

# Creating a dictionary
products_dict = {"AG32": 10,

Creating a dictionary

# Creating a dictionary
products_dict = {"AG32": 10, "HT91": 20,

Creating a dictionary

# Creating a dictionary
products_dict = {"AG32": 10, "HT91": 20, 
                 "PL65": 30, "OS31": 15, 
                 "KB07": 25, "TR48": 35

Creating a dictionary

# Creating a dictionary
products_dict = {"AG32": 10, "HT91": 20, 
                 "PL65": 30, "OS31": 15, 
                 "KB07": 25, "TR48": 35}

Accessing a value based on the key

Dictionaries are ordered
- Allows values to be accessed by subsetting on the key
What is the price of product ID "AG32"?

# Find the product's price
products_dict["AG32"]

Accessing all values

# Get all values from a dictionary
products_dict.values()

dict_values([10, 20, 30, 15, 25, 35])

Accessing all keys

# Retrieve all keys in a dictionary
products_dict.keys()

dict_keys(['AG32', 'HT91', 'PL65', 'OS31', 'KB07', 'TR48'])

Viewing an entire dictionary

# Print the dictionary
print(products_dict)

{'AG32': 10, 'HT91': 20, 'PL65': 30, 'OS31': 15, 'KB07': 25, 'TR48': 35}

# Get all items (key-value pairs)
products_dict.items()

dict_items([('AG32', 10), ('HT91', 20), ('PL65', 30), ('OS31', 15), ('KB07', 25),
('TR48', 35)])

.items() is useful when iterating or looping

Adding a key-value pair

# Add a new key-value pair
products_dict["UI56"] = 40

Updating a value

# Updating a value associated with an existing key
products_dict["HT91"] = 12

Duplicate keys

# Creating a dictionary with a duplicate key
products_dict = {"AG32": 10, "AG32": 20, 
                 "PL65": 30, "OS31": 15, 
                 "KB07": 25, "TR48": 35}


# Print the duplicate key's value
print(products_dict["AG32"])

Let's practice!

Introduction to Python for Developers