Have you ever wondered why your Python function keeps “remembering” old values between calls?
That’s the mysterious side of default parameters — a feature that can make your code cleaner and more flexible, but can also introduce subtle, confusing bugs if used incorrectly.
In this guide, you’ll learn:
How to use default parameters effectively
Common mistakes that even experienced developers make
Best practices to write predictable, bug-free functions
Starting Simple: Ohm’s Law in Python
Let’s begin with a simple, real-world example: Ohm’s Law.
If you’re not familiar with it, Ohm’s Law is a basic principle in electricity stating that current (I) = voltage (V) / resistance (R). I chose this example because it’s simple, intuitive, and perfect for illustrating how default parameters work in Python.
Here’s a function that applies Ohm’s Law:
def ohms_law_current(voltage, resistance): current = voltage/resistance return current
