Python Dictionaries: Organizing Data with Key-Value Pairs

Understanding Dictionaries: Real-World Connection

Imagine you have student information scattered across different pages - names on one page, ages on another, and ID card numbers on yet another page - every time you need complete information about one student, you'd have to flip through multiple pages and match positions, which is cumbersome and error-prone, just like how storing data in separate lists makes access difficult and inefficient. Dictionaries solve this by keeping each student bio-da (name, age, ID) is organized together in one page with clear labels, making it instantly accessible and meaningful without the hassle of cross-referencing multiple lists/pages.

Another Analogy is that its like having a physical phone book. You look up someone's name (the key) to find their phone number (the value). Or think of a real dictionary where you look up a word (key) to find its meaning (value). Python dictionaries work exactly the same way! They store data in key-value pairs where:

• Key: The label you use to find information (like a name or word)
• Value: The actual information stored (like a phone number or definition) 

Dictionary Creation Accessing Dictionary Data

Dictionaries are created using curly braces { } with key-value pairs separated by colons

To retrieve values from a dictionary, you can use square brackets [] with the key name for direct access, or use the get() method for safer access that won't crash your program if the key doesn't exist."

# Restaurant menu Creation
# dict_variable = { 'key1' : value1 , 'key2' : value2}
menu = {
    "burger": 250,
    "pizza": 400,
    "pasta": 300,
    "salad": 150,
    "coffee": 80
}
# Accessing values using keys
print(f"Burger costs: ₹{menu['burger']}")     # Output: Burger costs: ₹250
print(f"Pizza costs: ₹{menu['pizza']}")       # Output: Pizza costs: ₹400
# Safe way using get() method
price = menu.get("ice_cream")
print(price)                                  # Output: None (no error!)
coffee_price = menu.get("coffee")
print(coffee_price)                           # Output: 80

Dictionary vs List: When to Use What

Accessing Dictionary Data

There are two main ways to read data from dictionaries, each with different behaviours:

Method 1: Using Square Brackets [ ]

menu = {"burger": 250, "pizza": 400, "pasta": 300}
# Direct access - fast and straightforward
burger_price = menu["burger"]
print(f"Burger costs: ₹{burger_price}")  # Output: Burger costs: ₹250
# But be careful! This will crash if key doesn't exist
ice_cream_price = menu["ice_cream"]  # KeyError! > as the ice_cream is not exist in our dict

Method 2: Using .get() Method

menu = {"burger": 250, "pizza": 400, "pasta": 300}
# Safe access - never crashes
burger_price = menu.get("burger")
print(f"Burger price: ₹{burger_price}")  # Output: Burger price: ₹250
# Returns None if key doesn't exist (no crash!)
ice_cream_price = menu.get("ice_cream")
print(f"Ice cream price: {ice_cream_price}")  # Output: Ice cream price: None

Key Differences: [ ] vs .get()

Coming Up Next

You'll learn how to automatically process every item in your lists and dictionaries, making your programs incredibly powerful and efficient!

Loops are where programming becomes truly powerful - get ready to automate tasks that would take hours to do manually! 🔥