Introduction to Functions

Functions are reusable blocks of code designed to perform specific tasks. They help reduce redundancy and make programs more organized.

In this lesson, you will learn how to define, call, and use functions in Python.

What is a Function?

A function is a named section of code that performs a specific task. Functions can take inputs, process data, and return outputs.

For example:

# Defining a simple function
def greet():
    print("Hello, World!")

Defining a Function

You define a function using the def keyword, followed by the function name and parentheses:

The code inside the function will only execute when the function is called.

# Defining a function
def greet():
    print("Hello!")

Calling a Function

To use a function, you call it by its name followed by parentheses:

This runs the code inside the function.

# Calling a function
def greet():
    print("Hello!")

greet()

Using Parameters in Functions

Parameters are inputs that you can pass to a function to customize its behavior. For example:

# Function with parameters
def greet(name):
    print(f"Hello, {name}!")

greet("Alice")

Using Multiple Parameters

Functions can take multiple parameters:

Here, a and b are parameters.

# Function with multiple parameters
def add(a, b):
    print(a + b)

add(3, 5)

Keyword Arguments

You can use keyword arguments to specify parameter values by name:

# Function with keyword arguments
def greet(name, age):
    print(f"Hello, {name}. You are {age} years old.")

greet(age=30, name="Alice")

def multiply(a, b):
    return a * b

result = multiply(2, 4)
print(result)

Best Practices for Functions

Here are some best practices for using functions:

• Use descriptive names for functions and parameters.
• Keep functions short and focused on a single task.
• Avoid redundant code by reusing functions.

What Did We Learn?

In this lesson, you learned:

• What functions are and how to define them.
• How to call functions with parameters and keyword arguments.
• Best practices for writing clean and reusable functions.

Great job! Let’s move to the next lesson.