Python Functions Explained: Parameters, Type Hints, and Return Values

Understanding Functions in Python

Functions allow you to organize code into reusable blocks. In this article, you’ll learn how to define functions in Python, use parameters, apply type hints, and handle return values. Whether you’re a beginner or transitioning from Mojo, this guide will give you a strong foundation.

Basic Function Syntax

A basic Python function uses the def keyword followed by the function name and parameters:

def greet(name):
    return "Hello, " + name

This function takes a single argument name and returns a greeting string.

Multiple Parameters

Functions can accept multiple parameters, separated by commas:

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

You can call this function like add(2, 3) and get the result 5.

Default Parameter Values

Python supports default values for optional parameters:

def greet(name="World"):
    return "Hello, " + name

greet() will return "Hello, World".

Using Type Hints

Python allows you to optionally add type hints to improve code readability and catch type-related bugs:

def add(a: int, b: int) -> int:
    return a + b

These hints do not enforce types at runtime but help with static analysis tools like mypy.

Return Values

A function can return any data type. If no return statement is used, it returns None by default.

def log_message(msg: str) -> None:
    print(msg)

Anonymous Functions (Lambda)

Python supports simple one-line anonymous functions using lambda:

square = lambda x: x * x
print(square(4))  # Outputs: 16

Summary

• Define functions using def keyword
• Use parameters with or without default values
• Type hints improve clarity but are optional
• Return values can be of any type, including None

In the next article, we’ll compare Python and Mojo side-by-side to highlight key syntax differences.