Python User Defined Functions

Introduction

In Python, functions are reusable blocks of code that perform a specific task. User-defined functions allow you to write your own custom functions to organize your code better and avoid repetition. Functions can accept input parameters, perform operations, and return results.

Function Syntax

A function is defined using the def keyword, followed by the function name, parentheses (), and a colon :. The function body is indented below the definition.

Function को def keyword से define किया जाता है, उसके बाद function का नाम, parentheses (), और colon : आता है। Function का body indent करके लिखा जाता है।

def function_name(parameters):
    # function body
    statements

Example: Simple Function

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

greet()

This function greet() prints a welcome message when called.

यह greet() function कॉल करने पर एक स्वागत संदेश प्रिंट करता है।

Hello, welcome to Python functions!

Function Parameters and Arguments

Functions can accept inputs called parameters (or arguments) which allow them to perform tasks with different data.

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

greet("Anita")

Output:

Hello, Anita!

Return Values

Functions can return values back to the caller using the return statement.

Functions return स्टेटमेंट का उपयोग करके मान वापस कर सकते हैं।

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

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

Output:

Default Parameter Values

You can assign default values to parameters. If the caller does not provide those arguments, the default values are used.

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

greet()
greet("Ravi")

Output:

Hello, Guest! Hello, Ravi!

Keyword Arguments

You can call functions using parameter names explicitly, allowing arguments in any order.

def info(name, age):
    print(f"Name: {name}, Age: {age}")

info(age=30, name="Sunita")

Output:

Name: Sunita, Age: 30

Variable Length Arguments

Functions can accept arbitrary number of arguments using *args for positional and **kwargs for keyword arguments.

Functions *args का उपयोग करके अनिश्चित संख्या में position arguments, और **kwargs का उपयोग करके keyword arguments स्वीकार कर सकते हैं।

def sum_all(*args):
    total = 0
    for num in args:
        total += num
    return total

print(sum_all(1, 2, 3, 4))

Output:

Function Scope

Variables declared inside a function are local to that function and cannot be accessed outside it. Variables outside functions are global.

def demo():
    x = 10  # local variable
    print(x)

demo()
# print(x)  # Error: x is not defined outside the function

Output:

Why Use Functions?

Code reuse and organization
Break complex problems into smaller tasks
Make code easier to read and maintain
Avoid repetition