Functions — Reusable Code Blocks

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

result = greet("Alice")  # "Hello, Alice!"

Default parameters:

def greet(name, greeting="Hello"):
    return f"{greeting}, {name}!"

greet("Bob")            # "Hello, Bob!"
greet("Bob", "Hi")     # "Hi, Bob!"

*args — variable positional arguments:

def add_all(*numbers):
    return sum(numbers)

add_all(1, 2, 3, 4)  # 10

**kwargs — variable keyword arguments:

def display(**info):
    for key, value in info.items():
        print(f"{key}: {value}")

display(name="Alice", age=30)

Lambda — anonymous one-line functions:

square = lambda x: x ** 2
square(5)  # 25

numbers.sort(key=lambda x: x[1])  # sort by second element

Reference:

Wikipedia: Function

https://en.wikipedia.org/wiki/Function_(computer_programming)