Define and use procedures and functions, with or without parameters

📚 Programming: Procedures & Functions

What is a Procedure?

A procedure (also called a subroutine) is a block of code that performs a specific task but does not return a value. Think of it as a recipe that tells the computer how to bake a cake, but it doesn’t give you the cake itself.

What is a Function?

A function is similar to a procedure, but it returns a value after execution. It’s like a vending machine: you give it coins (arguments) and it gives you a snack (return value).

Parameters & Arguments

Parameters are placeholders in a procedure/function definition. Arguments are the actual values you pass when you call it.

• Procedure example: def greet(name):
• Function example: def add(a, b):

Return Values

Only functions can return values. Use the return statement to send data back to the caller.

Example: return a + b sends the sum of a and b back.

Comparison Table

Example: Calculating the Area of a Circle

We’ll write a function that takes the radius as a parameter and returns the area.

def circle_area(radius):
    """Return the area of a circle with the given radius."""
    pi = 3.14159
    return pi * radius * radius

Usage:

r = 5
area = circle_area(r)
print(f"The area of a circle with radius {r} is {area:.2f}")

Mathematically: $A = \pi r^2$

Practice Problems

1. Write a procedure print_hello that prints “Hello, world!”.
2. Write a function multiply(a, b) that returns the product of two numbers.
3. Write a function fahrenheit_to_celsius(f) that converts a temperature from Fahrenheit to Celsius.
4. Write a procedure display_menu() that prints a simple menu of options.
5. Write a function is_even(n) that returns True if n is even, otherwise False.

Summary

Procedures are like recipes that perform actions; functions are like vending machines that return a value. Both use parameters to accept input, but only functions use return to send data back. By mastering these concepts, you’ll be able to write cleaner, reusable code and solve problems more efficiently. 🚀