Python Functions

A function is a named block of code that performs a specific task, like a mini-program inside your main program. It lets you group related instructions together so you can run them whenever needed without rewriting the same lines over and over. Think of it as a vending machine: you input something (like coins), and it outputs something useful (like a snack) based on its built-in rules. Functions make your code cleaner and more efficient, especially as projects grow bigger.

Description: This is where you create the instructions for a specific task. You use the keyword def to tell Python you are starting a new set of instructions that you want it to remember for later.

def greet_user():
    print("Hello! Welcome to our website- estudy247.com")

Calling a Function

Defining a function doesn’t actually run the code; it just stores it. You tell Python to execute those saved instructions.

Description: To make a function work, you simply type its name followed by parentheses (). This tells the program to jump to those instructions, run them, and then come back to where it left off.

def greet_user():
    print("Hello! Welcome to our website- estudy247.com")

# This actually triggers the "Hello!" message function
greet_user()  # output: Hello! Welcome to our website- estudy247.com

Function Arguments

Parameters are like input boxes for a function. They allow us to pass values into the function to use inside it.

Description: Arguments are placeholders you put inside the parentheses when you create the function. When you call the function, you provide the actual “ingredients” (data) you want the function to use.

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

personalized_greeting("Alice") # Output: Hello, Alice!

Function with Return Value

Some functions just perform a task (like printing text), but others create something and give it back to you. Think of a juice machine: you put in an orange (input), and it “returns” a glass of juice (output) for you to use elsewhere.

Description: The return keyword tells Python to send a result back to the part of the program that called it. This allows you to save the result of a function into a variable to use later.

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

total = add_numbers(5, 10)
print(total) #output: 15

Default Parameters

A Default Parameter is like a “backup” choice. If you don’t provide a specific value, the function will use the one you pre-selected as the standard.

Description: You set a default value in the function definition. If the user provides their own value, Python uses that; if they leave it blank, Python uses the default value you provided.

def make_coffee(type="Black"):
    print("Making a cup of " + type + " coffee.")

make_coffee()          # Uses default: Black
make_coffee("Latte")   # Uses your choice: Latte

Variable Number of Arguments

Sometimes we don’t know how many values will be passed. Using *args or **kwargs, a function can handle many inputs.

def total_score(*args):  # Collects all as a tuple
    return sum(args)

print(total_score(85, 92, 78))  # Outputs: 255
print(total_score(100))  # Outputs: 100 (just one)

Nested Function

We can define a function inside another function. This is called a nested function and is useful for organizing code.

def outer():
    def inner():
        print("Inner function")
    inner() #outer function calls inner function
    print("Outer function")
outer() #outer function is called

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