Python Dictionaries Fundamentals

What is a Dictionary?

• A dictionary is an unordered collection of key-value pairs, where keys are unique and values can be of any data type.
• It is a mutable data structure, meaning it can be modified after creation.

Key Features of Dictionaries

• Keys: Must be immutable (e.g., strings, integers, tuples) and unique.
• Values: Can be of any data type, including strings, integers, lists, and other dictionaries.
• Key-Value Pairs: Each key is associated with a specific value.

Creating a Dictionary

• Can be created using the {} syntax, with key-value pairs separated by commas.
• Example: my_dict = {"name": "John", "age": 30}

Accessing and Modifying Dictionary Elements

• Accessing: Use the key to access the corresponding value, e.g., my_dict["name"].
• Modifying: Update a value by assigning a new value to an existing key, e.g., my_dict["age"] = 31.
• Adding: Add a new key-value pair, e.g., my_dict[" occupation"] = "Developer".
• Removing: Use the del statement to remove a key-value pair, e.g., del my_dict["age"].

Dictionary Methods

• keys(): Returns a list of all keys in the dictionary.
• values(): Returns a list of all values in the dictionary.
• items(): Returns a list of all key-value pairs in the dictionary.
• get(): Returns the value for a given key, or a default value if the key is not present.
• update(): Updates the dictionary with new key-value pairs.

Dictionary Operations

• Membership Testing: Use the in operator to check if a key is present in the dictionary, e.g., "name" in my_dict.
• Dictionary Concatenation: Not supported, as dictionaries are unordered and cannot be concatenated.

Dictionary Use Cases

• Configuration Files: Dictionaries are often used to store configuration settings, e.g., user preferences.
• Data Storage: Dictionaries can be used to store and manipulate data, such as user information or game state.
• Caching: Dictionaries can be used as a cache to store frequently accessed data.