If you’ve ever wondered how to convert a decimal number (like 25) into binary (like 11001), you’re not alone. It’s one of those foundational concepts in programming that sounds harder than it actually is.
Let’s break it down and see how Python makes this task super simple.
What Is Decimal and Binary Anyway?
Before we dive into code, it helps to understand the basics.
-
Decimal is the number system we use in everyday life. It’s based on 10 digits: 0 through 9.
-
Binary is the language of computers. It only uses two digits: 0 and 1.
When you convert from decimal to binary, you’re essentially rewriting the number in a form that computers can work with more directly.
The Quick Python Way
Python actually has a built-in function for this. If you just want a fast conversion, here it is:
If you run that, you’ll see the output:
What’s that 0b in front? That just tells you it’s a binary number. If you only want the binary digits, you can slice it off like this:
Now the output is:
Much cleaner, right?
Writing Your Own Conversion Function
Let’s say you want to go one step further and write the conversion from scratch. This is a great way to understand how the process works behind the scenes.
Here’s a simple function that does exactly that:
Let’s test it:
This function works by repeatedly dividing the number by 2 and collecting the remainders. When you reverse those remainders, you get the binary representation.
Why Bother Writing It Yourself?
Even though Python gives you built-in tools like bin(), writing it yourself teaches you how binary actually works. It’s a great exercise for beginners and helps you build a stronger understanding of number systems, loops, and string manipulation.
Wrapping Up
Whether you use Python’s built-in bin() function or write your own logic, converting decimal to binary is a skill worth knowing. It’s not just about numbers — it’s about thinking like a programmer and understanding how computers interpret the world.
If you’re new to Python, try tweaking the code, test it with different numbers, and even go the other way — convert binary back to decimal. Once you get the hang of this, a whole world of low-level logic and computer science concepts starts to open up.