Course Content

Python Functions Tutorial

1. What is a Function in Python?

What Is Function?Challenge: Building Functions Arguments Return Value Function Body Built-in Functions

2. Positional and Optional Arguments

Positional Arguments Challenge: Positional Arguments Optional Arguments Challenge: Optional Arguments

3. Arbitrary Arguments

Arbitrary Arguments Arbitrary Keyword Arguments Combination of Positional and Optional Arguments

4. Function Return Value Specification

Single Return Value Multiple Return Values None Return Value Generator Functions Challenge: Traffic lights

5. Recursion and Lambda Functions

Recursion Challenge: Search Engine Lambda Functions Immediately Invoked Lambda Expression Writing Effective and Maintainable Functions

Combination of Positional and Optional Arguments

Consider a function designed to calculate the total cost of smartphones, allowing you to specify various attributes during both initialization and function invocation.


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def calculate_smartphone_cost(model, price, quantity=1, discount=0):
    total_cost = price * quantity
    discount_amount = total_cost * (discount / 100)
    discounted_cost = total_cost - discount_amount
    
    print(f"Model: {model}")
    print(f"Unit price: ${price}")
    print(f"Quantity: {quantity}")
    print(f"Total cost before discount: ${total_cost}")
    
    if discount > 0:
        print(f"Discount: {discount}%")
        print(f"Discount amount: ${discount_amount}")
        print(f"Discounted cost: ${discounted_cost}")
    else:
        print("No discount applied.")
        print(f"Final cost: ${discounted_cost}")
    
    print()

# Examples of using the function
calculate_smartphone_cost("iPhone 13", 1099, 2)
calculate_smartphone_cost("Samsung Galaxy S21", 999, 1, 10)
calculate_smartphone_cost("Google Pixel 6", 799, quantity=3, discount=5)

Rules for Specifying Arguments

Positional Arguments

Positional arguments must be specified in the order they are defined in the function declaration. For example, in the function calculate_smartphone_cost, model and price are mandatory positional arguments.

Optional (Named) Arguments

Optional arguments can be specified either positionally or using named parameters. In the example, quantity and discount are optional arguments with default values that can be altered using named parameters during function invocation.

Default Values

If an optional argument is not specified during function call, its default value will be used. For instance, in the calculate_smartphone_cost function, if quantity and discount are not provided, they automatically take the values 1 and 0, respectively.

Named Parameters

Named parameters allow precise specification of values for optional arguments and determine their order of appearance. This enhances code clarity and readability, especially when dealing with multiple optional parameters.

This example and the rules for specifying arguments illustrate how to effectively use a combination of positional and named (optional) arguments to create functions that offer flexibility and ease of use, while maintaining code clarity and expected behavior.

1. What is the combination of positional and optional arguments in functions?

2. How do you define a function with positional arguments followed by optional arguments?

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Section 3. Chapter 3