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Python Basics in English / of Basics Introduction

Python: Price Calculation — Side-by-Side Patterns

Basic Structure

Theory:
  • All logic is written inline. Great for quick demos but hard to reuse or test.
  • Variables hold data; operations (like *) compute results; print shows output.
  • Use this when you want the simplest possible example with minimal structure.
book_price = 20
quantity = 2

total = book_price * quantity

print('Total Amount: ', total)

Function based design

Theory:
  • Encapsulates logic inside a function for reuse and testing.
  • Inputs become parameters (book_price, quantity); output can be returned or printed.
  • Use this when there is one clear operation and you want to call it multiple times.
def calculate_product_price(book_price, quantity):

    total = book_price * quantity

    print('Total Amount: ', total)

calculate_product_price(20, 3)

Class based design

Theory:
  • Object-oriented: bundle data (name) and behavior (calulate_price, display_details).
  • Great when you have multiple related operations for the same entity (Product).
  • Scale with more methods (discounts, taxes) and maintain state within objects.
class Product:
    def __init__(self):
        self.name = "Sairam"

    def calulate_price(self, book_price, quantity):

        total = book_price * quantity

        print('Total Amount: ', total, self.name)

    def display_details(self):
        print("Product name", self.name)

obj = Product()
obj.calulate_price(20, 3)
obj.display_details()

Production Code

Theory:
  • Adds logging for observability: info for business flow, debug for troubleshooting.
  • Type hints (float, int, None) communicate intent and work with linters.
  • Suitable for real projects where auditability and maintainability matter.
import logging

# Configure logging
logging.basicConfig(
    level=logging.INFO,
    format="%(asctime)s - %(levelname)s - %(message)s"
)


class Product:
    def __init__(self, name: str):
        self.name: str = name
        logging.info(f"Product initialized with name: {self.name}")

    def calculate_price(self, book_price: float, quantity: int) -> float:
        logging.info(f"Calculating price for {self.name}")
        logging.debug(f"Book Price: {book_price}, Quantity: {quantity}")

        total: float = book_price * quantity
        logging.info(f"Total Amount: {total} for {self.name}")

        return total

    def display_details(self) -> None:
        logging.info(f"Displaying product details for {self.name}")
        logging.info(f"Product Name: {self.name}")


# Example usage
if __name__ == "__main__":
    obj = Product(name="Sairam")
    obj.calculate_price(book_price=20, quantity=2)
    obj.display_details()