🛠️ Functions in Python | Lesson 10

🛠️ Functions in Python

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Functions are reusable blocks of code that perform a specific task. They help you write cleaner, modular, and organized programs. Instead of repeating code, you write a function once and use it whenever needed! Let’s explore how to create and use functions. 🚀

What is a Function? 🤔

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A function is a named block of code designed to do a particular job. Functions can take inputs, do some processing, and optionally return a result.

1. Defining a Function 🔧

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Use the def keyword, followed by the function name and parentheses.

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

To call the function and run its code:

greet()  # Output: Hello, World!

2. Function Parameters and Arguments 🎯

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Functions can take parameters (inputs) to make them flexible.

def greet(name):
    print(f"Hello, {name}!")

Call with an argument:

greet("Anita")  # Hello, Anita!

3. Returning Values 🔄

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Functions can send back a result using the return statement.

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

result = add(5, 3)
print(result)  # 8

4. Default Parameters 🎁

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Functions can have default values for parameters.

def greet(name="Friend"):
    print(f"Hello, {name}!")

greet()          # Hello, Friend!
greet("Rahul")   # Hello, Rahul!

5. Keyword Arguments 🗝️

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You can specify arguments by name.

def describe_pet(name, animal="dog"):
    print(f"{name} is a {animal}.")

describe_pet(animal="cat", name="Milo")  # Milo is a cat.

Practice Questions with Solutions 🏆

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1. Practice: Write a function square() that returns the square of a number.
   • Solution:

def square(num):
    return num * num
print(square(4))  # 16

2. Practice: Write a function is_even() that checks if a number is even and returns True or False.
   • Solution:

def is_even(n):
    return n % 2 == 0

print(is_even(7))  # False
print(is_even(8))  # True

3. Practice: Create a function greet that prints “Welcome!” if no name is given or “Welcome, !” if a name is provided.
   • Solution:

def greet(name=""):
    if name:
        print(f"Welcome, {name}!")
    else:
        print("Welcome!")

greet()
greet("Anil")

Step-by-Step Mini Project: Calculator Functions 🔢

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Write functions for add, subtract, multiply, and divide, then use them.

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

def subtract(a, b):
    return a - b

def multiply(a, b):
    return a * b

def divide(a, b):
    if b != 0:
        return a / b
    else:
        return "Error! Division by zero."

print(add(10, 5))        # 15
print(divide(8, 0))      # Error! Division by zero.

Checklist for This Chapter ✅

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• Defined and called functions
• Used parameters and arguments
• Returned values from functions
• Used default and keyword arguments

You now know how to create and use functions to keep your programs neat, reusable, and efficient! Start practicing by building calculators, converters, and games! 🎉