Functions in Python Programming

In this tutorial, we will learn about Functions, which are one of the most fundamental building blocks in Python programming. They allow you to organize your code into reusable blocks, making it modular and easier to maintain.
I will guide you through a straightforward and engaging method that makes even complex concepts easy. With clear code examples and illustrative output.

What is a Function?

A function in Python is a reusable block of code designed to perform a specific task. It can take inputs (arguments), process them, and return an output. Functions help in reducing redundancy and improving the readability of your code.

Example 1: A Simple Function

Let’s create a function that says “Hello, World!”:

def say_hello():
    print("Hello, World!")

say_hello()

Explanation:

1.  This defines a function named “say_hello()”. The parentheses () indicate that this function does not take any input arguments.

2.  Inside the function, we tell Python to print “Hello, World!” whenever the function is called.

3.  This is how we call (or use) the function. When we call it, the code inside the function runs

Output:

Hello, World!

Example 2: Function with Arguments

Now, let’s make a function that adds two numbers together. We’ll tell the function what numbers to add each time we use it.

def add_numbers(a, b):
    print(f"The sum of {a} and {b} is {a + b}")

add_numbers(5, 3)

Explanation:

1.  This defines a function named “add_numbers” that takes two inputs (arguments): a and b.

2.  Inside the function, we calculate the sum of a and b using “a + b”, then print the result in a sentence.

3. When we call the function with 5 and 3, these values are assigned to a and b, respectively. The function calculates their sum (5 + 3 = 8) and prints it.

Output:

The sum of 5 and 3 is 8

Example 3: Using the return Statement

Sometimes, we want our function to give us back a result instead of just printing it. Let’s make a function that multiplies two numbers and returns the result.

def multiply_numbers(x, y):
    return x * y

result = multiply_numbers(4, 5)
print(f"The product is {result}")

Explanation:

1. This defines a function named “multiply_numbers” that takes two inputs (x and y) and returns their product.

2.  Instead of printing the result directly, the function sends back (returns) the result to wherever it was called.

3. Here, we call the function with inputs 4 and 5. The function calculates their product (4 * 5 = 20) and returns it. The returned value (20) is stored in the variable result.

4. Finally, we print the value stored in result.

Output:

The product is 20

Example 4: Default Parameters

What if we want a function to have a default value if we don’t provide one? Let’s make a greeting function that says “Hello, Guest!” if we don’t specify a name.

def greet(name="Guest"):
    print(f"Hello, {name}!")

greet()

greet("Alice")

Explanation:

1.  This defines a function named greet. It has one parameter called name, which has a default value of  ” Guest”. If no value is provided for name, it will use “Guest”.

2. greet(): When we call the function without any argument, it uses the default value “Guest” and prints “Hello, Guest!”.

3.  greet(“Alice”): When we call the function with “Alice”, it overrides the default value and prints “Hello, Alice!”.

Output:

Hello, Guest! 
Hello, Alice!

Example 5: Lambda Functions

Lambda functions are short, one-line functions. Let’s make a simple lambda function that adds two numbers.

add = lambda x, y: x + y
print(f"The sum is {add(7, 3)}")

Explanation:

1. A lambda function is a short way to define small functions without using ” def “.

2. We call this lambda function using its name (add) with inputs 7 and 3. It calculates their sum (7 + 3 = 10) and returns it.

3. The returned value (10) is printed.

output:

The sum is 10