Collections

Handle Groups of Data the Right Way

Python gives us powerful built-in data structures to handle groups of items. Whether you’re storing a list of fruits, a set of unique tags, or a product catalog, Python’s collections have you covered.

🔢 1. Lists – Ordered & Mutable #

A list is an ordered collection of items that can be changed (mutable).

fruits = ['apple', 'banana', 'orange']

✅ Properties:

• Ordered (indexed)
• Allows duplicates
• Mutable (can add, remove, or change)

🔧 Common Operations:

fruits.append('grape')        # Add item
fruits.remove('banana')       # Remove item
fruits[0] = 'mango'           # Modify item
len(fruits)                   # Length of list

🧊 2. Tuples – Ordered & Immutable #

A tuple is like a list, but cannot be changed after creation.

coordinates = (10, 20)

✅ Properties:

• Ordered
• Allows duplicates
• Immutable (cannot modify elements)

📝 Useful for data that should not change, like coordinates or constants.

x, y = coordinates  # Tuple unpacking

🧹 3. Sets – Unordered & Unique #

A set stores unique items only and is unordered.

unique_fruits = {'apple', 'banana', 'apple'}
print(unique_fruits)  # {'banana', 'apple'}

✅ Properties:

• Unordered
• No duplicates
• Useful for filtering and comparison

🔧 Common Operations:

unique_fruits.add('mango')
unique_fruits.remove('banana')

🔁 Sets don’t support indexing like lists or tuples.

📚 4. Dictionaries – Key-Value Pairs #

A dictionary stores data as key: value pairs.

product = {
    'name': 'Milk',
    'price': 50,
    'stock': 20
}

✅ Properties:

• Unordered (in older Python versions), ordered from Python 3.7+
• Fast lookup by key
• Mutable

🔧 Common Operations:

product['price'] = 55
product['category'] = 'Dairy'
del product['stock']

🔄 5. Iterating Through Collections #

You can use for loops to iterate over all collection types.

List: #

for fruit in fruits:
    print(fruit)

Tuple: #

for coord in coordinates:
    print(coord)

Set: #

for item in unique_fruits:
    print(item)

Dictionary (keys, values, both): #

for key in product:
    print(key, product[key])

# OR
for key, value in product.items():
    print(key, "->", value)

🧠 When to Use What Collection Type? #

🛒 Real-World Use Case: Inventory System for a Grocery Store #

Let’s simulate a simple inventory system that:

• Stores products with prices and stock
• Allows adding and removing products
• Prints available inventory

✅ Code Example #

# Dictionary to store products
inventory = {
    'milk': {'price': 50, 'stock': 20},
    'bread': {'price': 30, 'stock': 15},
    'eggs': {'price': 10, 'stock': 100}
}

# Function to print inventory
def show_inventory():
    print("\n🛒 Available Inventory:")
    for item, info in inventory.items():
        print(f"{item.title()} - Rs.{info['price']} | Stock: {info['stock']}")

# Function to add a product
def add_product(name, price, stock):
    inventory[name.lower()] = {'price': price, 'stock': stock}
    print(f"✅ {name.title()} added to inventory.")

# Function to remove a product
def remove_product(name):
    if name.lower() in inventory:
        del inventory[name.lower()]
        print(f"❌ {name.title()} removed.")
    else:
        print(f"⚠️ {name.title()} not found.")

# Run a sample
show_inventory()
add_product("Butter", 60, 10)
remove_product("eggs")
show_inventory()

🧾 Sample Output #

🛒 Available Inventory:
Milk - Rs.50 | Stock: 20
Bread - Rs.30 | Stock: 15
Eggs - Rs.10 | Stock: 100
✅ Butter added to inventory.
❌ Eggs removed.

🛒 Available Inventory:
Milk - Rs.50 | Stock: 20
Bread - Rs.30 | Stock: 15
Butter - Rs.60 | Stock: 10

🧠 Key Takeaways #

🔚 Wrap Up #

Python collections are the backbone of data manipulation. Once you master them, you can build:

• Shopping carts 🛒
• To-do lists 📝
• User databases 🧑‍💼
• Product catalogs 📦
• And much more!

🔜 Coming Next: #

File Handling in Python
Learn how to read and write files, manage data from .txt or .csv, and build something practical like a Customer Order Tracker.

Want me to write that chapter too? Or package this one as a PDF/series for your site or YouTube content? Let me know!