Drop #10 – Writing Your Own Functions

Have you ever copied and pasted the same few lines of code multiple times?

Or changed one line in five places just to fix a bug?

That’s your cue: it’s time to write your own functions.

In Python, functions are the building blocks of clean, reusable, and testable code.

🛠️ Think of functions like tools

Imagine you're baking bread. You follow a recipe:

1. Add flour, water, yeast, salt.

2. Knead the dough.

3. Let it rise.

4. Bake it.

Now imagine coding this as a function:

With this function, you can now "bake bread" with any ammount of ingredients you want, without rewriting the process each time.

🔍 How to write a function in Python

Here’s the basic syntax:

Let’s say we want to calculate the area of a rectangle:

Now, instead of repeating in your code, you just call:

Simple, readable, and reusable.

🎯 Why return matters

The keyword sends a result back to wherever the function was called.

If you don’t return anything, the function still runs—but it returns by default.

Use when you want your function to produce a value you can reuse.

🚨 Common mistakes to avoid

• Forgetting to use when needed

• Using the same name for parameters and variables, causing confusion

• Writing functions that do too much — keep them focused

✅ Pro tip: Functions make your code testable

When logic is wrapped in functions, you can write unit tests for them in isolation — no UI, no manual steps, just pure logic. It’s a cornerstone of professional Python development.

Next up: – Python’s built-in way to store structured, labeled data.

This post is part of my ongoing Python Drops series.

Clear. Practical. Professional.

Helping you master Python — one drop at a time.

Tell me: What’s a small function you wrote recently that made your life easier?