Dictionaries: Key-Value Pairs

Learning Objectives Define what a dictionary is and explain its purpose in programming. Identify and differentiate between keys and values within a dictionary. Create dictionaries using appropriate syntax to store related data. Access, add, update, and remove data from dictionaries using their keys. Explain the difference between dictionaries and lists and when to use each. Demonstrate how to check for the existence of a key in a dictionary. Ever tried to find a friend's phone number in a messy notebook? 🤯 What if you could instantly find it just by knowing their name? In this lesson, you'll discover dictionaries, a powerful data structure that lets you organize information like a real-world dictionary or a phonebook. You'll learn how to store and retrieve d...

TermDefinitionExample DictionaryA collection of data that stores information in 'key-value' pairs. It's like a real-world dictionary where each word (key) has a definition (value).In Python: `{'apple': 'a fruit', 'banana': 'a yellow fruit'}` KeyA unique identifier used to look up a specific value in a dictionary. Keys must be immutable (like numbers, strings, or tuples).In `{'name': 'Alice', 'age': 14}`, 'name' and 'age' are keys. ValueThe data associated with a specific key in a dictionary. Values can be any data type (numbers, strings, lists, or even other dictionaries).In `{'name': 'Alice', 'age': 14}`, 'Alice' and 14 are values. Key-Value Pai...

Creating a Dictionary Dictionaries are defined using curly braces `{}` with key-value pairs separated by colons `:` and pairs separated by commas `,`. Use this syntax to initialize a new dictionary, either empty or with initial data. Example: `my_dict = {'key1': 'value1', 'key2': 'value2'}` Accessing Values To retrieve a value, use square brackets `[]` with the key inside: `dictionary_name[key]`. This is how you 'look up' a value using its unique key, similar to how you use an index for a list, but with a meaningful key instead of a number. Example: `my_dict['key1']` Adding/Updating Items To add a new key-value pair or update an existing one, assign a value to a key: `dictionary_name[new_key] = new_value`. I...