Module 11: Dictionaries

In this module, we will learn about Dictionaries. A dictionary stores data in Key-Value Pairs (like a phonebook where name is the Key and phone number is the Value).

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11.1 Introduction to Dictionaries

• A dictionary is created using curly braces { } with key: value pairs separated by commas.
• Keys must be unique (you cannot have duplicate keys).
• Dictionaries are Mutable (you can change values after creation).
• We access values using their corresponding keys instead of index numbers.

# Creating a dictionary
student = {
    "name": "Sai Kumar",
    "age": 22,
    "course": "Python",
    "is_certified": True
}

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11.2 Accessing Data

There are two ways to retrieve values from a dictionary:

1. Using Square Brackets:

print(student["name"]) # Output: Sai Kumar
# print(student["marks"]) # If the key does not exist, this throws a KeyError!

2. Using the get() Method (Safe Way):

# Returns "None" instead of throwing an error if the key is missing
print(student.get("marks")) # Output: None

# You can specify a default value to return if the key is missing
print(student.get("marks", 0)) # Output: 0

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11.3 Dictionary Methods

Common methods used to update and delete data in a dictionary:

# 1. Updating a value or adding a new key-value pair
student["age"] = 23 # Updates existing value
student["location"] = "Hyderabad" # Adds a new key-value pair
print(student)

# 2. keys() - Returns a list of all keys in the dictionary
print(student.keys()) 

# 3. values() - Returns a list of all values in the dictionary
print(student.values())

# 4. items() - Returns key-value pairs as a list of tuples
print(student.items())

# 5. pop() - Removes a specific key and its value
student.pop("is_certified")

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11.4 Nested Dictionaries

A dictionary inside another dictionary is called a Nested Dictionary. This is used to store complex data.

users = {
    "user1": {
        "name": "Sai",
        "role": "Admin"
    },
    "user2": {
        "name": "Ram",
        "role": "Editor"
    }
}

# Accessing Ram's role
print(users["user2"]["role"]) # Output: Editor

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11.5 JSON Thinking (Crucial for AI)

When working with APIs, web services, or Artificial Intelligence (AI) models, data is sent and received in a format called JSON (JavaScript Object Notation).

Python Dictionaries look and work almost exactly like JSON. Learning dictionaries helps you handle data easily when working with AI.

AI API Response Example:

An AI model (like Gemini or GPT) sends responses in a JSON structure that looks like this:

ai_response = {
    "model": "gemini-1.5-flash",
    "choices": [
        {
            "message": {
                "role": "assistant",
                "content": "Python is a high-level programming language."
            }
        }
    ],
    "usage": {
        "total_tokens": 150
    }
}

# How to extract the AI's answer:
result = ai_response["choices"][0]["message"]["content"]
print(result) 
# Output: Python is a high-level programming language.

Handling dictionaries is a key skill for building AI applications!