Python Build a Shopping List Manager

A household tracks items to buy before going to the store.

What You Need to Understand

A small shopping-list program can add products, avoid accidental duplicate entries, and display the current list. It combines list methods, conditionals and iteration.

When to Use It

A household tracks items to buy before going to the store.

Step-by-Step Python Example

shopping_list = []
for product in ["milk", "bread", "milk", "eggs"]:
    if product not in shopping_list:
        shopping_list.append(product)
for position, product in enumerate(shopping_list, start=1):
    print(f"{position}. {product}")

How the Example Works

The duplicate milk is skipped, and the remaining three items are numbered for display.

Example Output

1. milk
2. bread
3. eggs
['bread']

A Second Example

Compare this smaller variation with the main example, then experiment with your own values.

products = ["bread", "milk"]
to_remove = "milk"
if to_remove in products:
    products.remove(to_remove)
print(products)

Important Behavior and Edge Cases

List membership checks are linear, which is fine for a short shopping list. Normalize capitalization if Milk and milk should be treated alike.

Try It Yourself

Add a command that removes an existing product safely.

Common Beginner Mistakes

• List membership checks are linear, which is fine for a short shopping list. Normalize capitalization if Milk and milk should be treated alike.
• Overlooking how an iterable is consumed, how element positions are chosen, or whether a function creates a new list.

Key Takeaways

• A small shopping-list program can add products, avoid accidental duplicate entries, and display the current list.
• The duplicate milk is skipped, and the remaining three items are numbered for display.
• List membership checks are linear, which is fine for a short shopping list.