In Python (programming language), a function is a block of reusable code that performs a specific task.

Functions help to:

🔹 Defining a Function

In Python, functions are defined using the def keyword.

def function_name():
    # code block

🔹 Example: Simple Function

def greet():
    print("Hello, Welcome to Python!")greet()

Output:

Hello, Welcome to Python!

Here:

Functions can accept inputs called parameters.

def greet(name):
    print("Hello,", name)

greet("Rahul")

Output:

Hello, Rahul

Functions can return a value using the return keyword.

def add(a, b):
    return a + b

result = add(5, 3)
print(result)

Output:

You can give default values to parameters.

def greet(name="Guest"):
    print("Hello,", name)greet()
greet("Alice")

Output:

Hello, Guest
Hello, Alice

Python allows returning multiple values.

def calculate(a, b):
    return a + b, a - b

sum_result, diff_result = calculate(10, 5)
print(sum_result, diff_result)

Output:

15 5

A lambda function is a small, single-line function.

square = lambda x: x * x
print(square(5))

Output:

Variables inside a function are called local variables.
Variables outside are called global variables.

x = 10  # globaldef show():
    y = 5  # local
    print(x, y)show()