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Ex 21: Order Invoice Generator

Problem​

Build an automated restaurant invoice system that generates a detailed report for customers.

Rules​

  • Define generate_invoice(customer_name="Guest", *items, **charges) -> str.
  • *items accepts any number of positional arguments for food items.
  • **charges accepts any number of keyword arguments for costs like tax or service.
  • Sum only the values from **charges for the total amount.

Boilerplate​

Copy below code and paste to our IDE for head start.

# Write our code inside this function
def generate_invoice(customer_name="Guest", *items, **charges):
    pass # remove this

# Call with test data
print(generate_invoice("Amit", "Burger", "Fries", tax=50.0, service=20.0))

Expected Output​

Invoice for Amit:
Items:
- Burger
- Fries
Charges:
Tax: 50.0
Service: 20.0
Total Amount Due: ₹70.0

Solution​

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Show solution
def generate_invoice(customer_name: str = "Guest", *items: str, **charges: float) -> str:
    lines = [f"Invoice for {customer_name}:"]

    if items:
        lines.append("Items:")
        for item in items:
            lines.append(f"- {item}")

    if charges:
        lines.append("Charges:")
        for name, amount in charges.items():
            lines.append(f"{name.capitalize()}: {amount}")

    total = sum(charges.values())
    lines.append(f"Total Amount Due: ₹{total}")

    return "\n".join(lines)

# Test data
print(generate_invoice("Amit", "Burger", "Fries", tax=50.0, service=20.0))

Details​

Using *args and **kwargs provides maximum flexibility for our functions. Positional arguments (*items) are collected into a tuple, while keyword arguments (**charges) are collected into a dictionary, which makes calculating the total with sum(charges.values()) very straightforward.