Functions in Python

 A function is a block of reusable code that performs a specific task.

Functions help to avoid repetition and make programs organized and modular.

In Python, functions are created using the def keyword.

Advantages of using functions:

• Code reusability

• Easy debugging

• Better readability

• Reduces code length

• Improves program structure

Defining a Function

A function is defined using the def keyword followed by function name and parentheses.

Syntax:

def function_name():
    statements

Example:

def greet():
    print("Hello World")

greet()

Function with Parameters

Parameters are values passed to a function.

Syntax:

def function_name(parameter):
    statements

Example:

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

greet("Kumar")

Function with Return Value

The return statement sends a value back to the caller.

Syntax:

def function_name():
    return value

Example:

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

result = add(10, 5)
print(result)

Types of Arguments in Python

Python supports different types of arguments:

1. Positional Arguments

2. Keyword Arguments

3. Default Arguments

4. Variable-length Arguments

Positional Arguments

Values are passed in the correct order.

def student(name, age):
    print(name, age)

student("Arun", 20)

Keyword Arguments

Values are passed using parameter names.

def student(name, age):
    print(name, age)

student(age=20, name="Arun")

Default Arguments

A default value is assigned to a parameter.

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

greet()
greet("Ravi")

Variable-Length Arguments (*args)

Used when the number of arguments is unknown.

def total(*numbers):
    print(sum(numbers))

total(10, 20, 30)

Lambda Function

A lambda function is a small anonymous function.

Syntax:

lambda arguments: expression

Example:

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

Recursive Function

A function that calls itself is called recursion.

Example:

def factorial(n):
    if n == 1:
        return 1
    else:
        return n * factorial(n-1)

print(factorial(5))

Scope of Variables

Variable scope determines where a variable can be accessed.

Types:

• Local Variable

• Global Variable

Example:

x = 10  # Global

def show():
    y = 5  # Local
    print(x)
    print(y)

show()

Built-in Functions

Python provides many built-in functions such as:

• print()

• len()

• type()

• sum()

• max()

• min()

Example:

numbers = [10, 20, 30]
print(len(numbers))
print(max(numbers))

Conclusion

Functions are very important in Python programming. They:

✔ Improve code reusability
✔ Make programs modular
✔ Reduce repetition
✔ Increase readability

Without functions, programs become lengthy and difficult to manage.