Functions in Python are blocks of code that perform a specific task, and they can be defined using the def keyword.
Definition:

• A function in Python is a block of reusable code that performs a specific task.
• It allows you to break down your program into smaller, more manageable pieces, making your code modular and easier to understand.

Function Call:

• To use a function, you call it by its name followed by parentheses ().

Parameters and Arguments:

• Functions can accept input data called parameters.
• When calling a function, you provide the actual values, known as arguments, for these parameters.

Return Value:

• Functions can optionally return a value using the return statement. This value can then be used in the rest of your program.

In simple words-

• Function Definition: Define the function with its name and parameters.
• Function Call: When the function is called, the flow of control jumps to the function definition.
• Execute Function: Perform the tasks defined inside the function.
• Return Value (Optional): If there’s a return statement, the function returns a value to the caller.
• End: End of the function execution, control returns to the caller.

Imagine a Function as a MonsterMachine

Think of a function as a special machine in your Python code. You give it certain inputs (like ingredients for a recipe), it performs a specific task (like cooking the ingredients), and then it can optionally provide an output (like the delicious meal!).

Steps to Build Your Function MonsterMachine:

1. Name Your MonsterMachine: Choose a descriptive name for your function that reflects what it does. Let’s call our function greet.
2. Define the Inputs (if any): These are like the ingredients you feed into your machine. If your function needs information to complete its task, specify variables within parentheses after the function name. For example, sayhello(name). Here, name is the input variable. These are Function Parameters:- Functions can take zero or more parameters.You can have default values for parameters as well.
3. Tell Your MonsterMachine What to Do: Use Python code blocks to instruct your function what to accomplish with the inputs (or without them if there are none). Indentation is crucial here!
4. Optional Output: If your function needs to return a value, use the return statement. This is like the cooked meal your machine produces.

Let’s Code a Greeter Machine!

Here’s how we can create a function called greet that takes a name as input and prints a greeting:

Python

def sayhello(name):
  """Prints a greeting message to the user."""
  print("Hello,", name + "!")

# Now let's use our greeter machine!
sayhello("Alice")  # Output: Hello, Alice!

Experimenting with Your Machine

We can call the greet function multiple times with different names to see it work its magic:

Python

sayhello("Bob")  # Output: Hello, Bob!
sayhello("Charlie")  # Output: Hello, Charlie!

Challenge: Build a Pizza Order Machine!

Can you create a function called order_pizza that takes the size (small, medium, large) and the number of toppings (as an integer) as inputs, and then prints the pizza order details?

Here’s a hint:

Python

def order_pizza(size, num_toppings):
  # ... your code here ...

# Test your order_pizza function!
order_pizza("medium", 2)  # Output: You ordered a medium pizza with 2 toppings.