Python Programming

Functions in Python

Beginner Lesson 5 of 10

Functions in Python

Functions are reusable blocks of code that perform specific tasks.

Defining Functions

def greet(name):
    """Return a greeting message."""
    return f"Hello, {name}!"

message = greet("Alice")
print(message)  # Hello, Alice!

Parameters and Arguments

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

# Keyword arguments
greet(name="Bob", greeting="Hi")

# *args for variable positional arguments
def sum_all(*numbers):
    return sum(numbers)

# **kwargs for variable keyword arguments
def print_info(**kwargs):
    for key, value in kwargs.items():
        print(f"{key}: {value}")

Lambda Functions

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

# Common use with map, filter
numbers = [1, 2, 3, 4, 5]
squared = list(map(lambda x: x**2, numbers))

Next Steps

Continue to Object-Oriented Programming →