User Defined Functions in Python

A user-defined function in Python is a block of reusable code created using the def keyword. Functions help organize code, reduce repetition, and improve readability.

Python में user-defined function एक ऐसा block होता है जिसे हम खुद def की मदद से define करते हैं। ये कोड को दुबारा इस्तेमाल करने में मदद करता है और प्रोग्राम को organized बनाता है।

Advantages of User Defined Functions

• Code Reusability
• Better Code Organization
• Easy to Debug and Maintain
• Improves Readability

Types of User Defined Functions

• Without Parameters and Without Return Value
• With Parameters and Without Return Value
• Without Parameters and With Return Value
• With Parameters and With Return Value

Examples

1. Function with no parameter, no return value

   def greet():
       print("Hello, welcome!")
   
   greet()

   Output:

   Hello, welcome!

2. Print current year

   def show_year():
       print("Year: 2025")
   
   show_year()

   Output:

   Year: 2025

3. Function with parameter, no return

   def welcome(name):
       print("Hello", name)
   
   welcome("Abhishek")

   Output:

   Hello Abhishek

4. Add two numbers

   def add(a, b):
       print("Sum:", a + b)
   
   add(10, 5)

   Output:

   Sum: 15

5. No parameter, with return value

   def give_pi():
       return 3.14159
   
   print("Pi:", give_pi())

   Output:

   Pi: 3.14159

6. Return fixed name

   def get_name():
       return "Python"
   
   print(get_name())

   Output:

   Python

7. Parameter and return value

   def square(x):
       return x * x
   
   print("Square:", square(6))

   Output:

   Square: 36

8. Max of two numbers

   def maximum(a, b):
       return a if a > b else b
   
   print("Max:", maximum(10, 20))

   Output:

   Max: 20

9. Check even or odd

   def check_even(n):
       return "Even" if n % 2 == 0 else "Odd"
   
   print(check_even(7))

   Output:

   Odd

10. Factorial using function

    def factorial(n):
        f = 1
        for i in range(1, n+1):
            f *= i
        return f
    
    print("Factorial:", factorial(5))

    Output:

    Factorial: 120

11. Sum of list

    def list_sum(lst):
        return sum(lst)
    
    print(list_sum([1,2,3]))

    Output:

    6

12. Print stars

    def print_stars():
        for i in range(5):
            print("*")
    
    print_stars()

    Output:

    *
    *
    *
    *
    *

13. Table of number

    def table(n):
        for i in range(1, 11):
            print(n, "x", i, "=", n*i)
    
    table(4)

    Output:

    4 x 1 = 4
    ...
    4 x 10 = 40

14. Check prime

    def is_prime(n):
        if n < 2:
            return False
        for i in range(2, n):
            if n % i == 0:
                return False
        return True
    
    print(is_prime(7))

    Output:

    True

15. Global and local variable

    x = 50
    
    def show():
        x = 10
        print("Local x:", x)
    
    show()
    print("Global x:", x)

    Output:

    Local x: 10
    Global x: 50

16. Nested function

    def outer():
        def inner():
            print("Inside inner")
        print("Inside outer")
        inner()
    
    outer()

    Output:

    Inside outer
    Inside inner