Python Functions: Learn with Practical Examples | FACE Prep

Python Functions: Learn with Practical Examples | FACE Prep

Functions in Python: A Complete Guide

Functions in Python are blocks of organized and reusable code designed to perform specific tasks. Simply put, a function takes inputs, processes them, and returns a result. In this article, we’ll explore functions in Python, their importance, types, and examples, all while aligning with current trends for clarity and SEO optimization.Python Functions

Why Do We Need Functions in Python?

Functions make code more modular, reusable, and readable. Consider the problem of finding two numbers in a list whose sum equals a given number. Without functions, the code might look cumbersome:
# Without functions
list1 = [3, 6, 4, 9]
res1 = list1[0] + list1[1]
if res1 == 13:
    print(list1[0], list1[1])
# Repeated code...
The above approach is repetitive and inefficient. Using functions, this can be optimized:
# With functions
def find_pairs(lst, target):
    for i in range(len(lst)):
        for j in range(i + 1, len(lst)):
            if lst[i] + lst[j] == target:
                print(lst[i], lst[j])

list1 = [3, 6, 4, 9]
find_pairs(list1, 13)

Arguments and Parameters in Functions

Arguments

Arguments are values passed to a function when it is called. They act as resources for the function to complete its task.

Parameters

Parameters are variables defined in the function signature to accept arguments passed during the function call.

Types of Functions in Python

  1. Built-in Functions: Predefined in Python, such as print(), len(), and sum().
  2. User-defined Functions: Functions created by the user to address specific needs.

How to Define a Function in Python

Step 1: Defining the Function

To define a function, use the def keyword, followed by the function name and a colon:
def function_name(parameters):
    # Function body
    pass

Step 2: Calling a Function

A function is executed only when called:
def greet(name):
    print(f"Hello, {name}!")

greet("Alice")

Step 3: Returning Results

A function can either print or return a result:
def add(a, b):
    return a + b

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

Examples of Functions in Python

Example 1: Function with Return

def square(num):
    return num ** 2

print(square(4))

Example 2: Nested Functions

Python allows functions within functions, also known as nested functions:
def outer_function(text):
    def inner_function():
        return text.upper()
    return inner_function()

print(outer_function("hello"))

Advanced Concepts in Functions

a) Call by Reference

Python uses “call by reference,” meaning parameters and arguments share the same memory location.
def modify_list(lst):
    lst.append(10)

my_list = [1, 2, 3]
modify_list(my_list)
print(my_list)  # Output: [1, 2, 3, 10]

b) Returning Multiple Values

A function can return multiple values, packed as a tuple:
def calculate(a, b):
    return a + b, a - b

sum_, diff = calculate(5, 3)
print(f"Sum: {sum_}, Difference: {diff}")

c) Recursive Functions

Functions that call themselves to solve smaller subproblems:
def factorial(n):
    if n == 0:
        return 1
    return n * factorial(n - 1)

print(factorial(5))

FAQs About Functions in Python

1. What are Functions in Python?

Functions are reusable blocks of code that perform a specific task.

2. How Do You Define Functions in Python?

Use the def keyword followed by the function name and a colon. Define the logic inside an indented block.

3. What are Built-in Functions?

Predefined functions like print(), len(), and type() available in Python’s standard library.

4. Can a Function Return Multiple Values?

Yes, by separating them with commas.
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