I was working on a project where I needed to extract the first digit of a number in Python. At first, it sounds simple, but depending on the approach you use, there are multiple ways to solve this.
As someone who has been writing Python code for more than 10 years, I’ve faced this requirement many times. Whether I was building a data-cleaning script for financial data or parsing numeric IDs in a U.S.-based customer database, quickly obtaining the first digit became essential.
In this tutorial, I’ll show you four easy methods to get the first digit of a number in Python. I’ll also share my firsthand experience with each method so you can decide which one is best for your project.
Method 1 – Convert Number to String and Slice
The easiest way to get the first digit is to convert the number into a Python string and then take the first character.
Here’s how I do it:
# Method 1: Using string slicing
num = 98765
# Convert to string and get the first character
first_digit = int(str(num)[0])
print("The first digit is:", first_digit)Output:
The first digit is: 9I executed the above example code and added the screenshot below.
This method is super quick and works well when you’re dealing with integers. I often use it when parsing U.S. ZIP codes stored as integers in a dataset.
Method 2 – Use a While Loop
Another method is to repeatedly divide the number by 10 until only one digit remains.
Here’s the code:
# Method 2: Using while loop
num = 98765
while num >= 10:
num //= 10 # Integer division
print("The first digit is:", num)Output:
The first digit is: 9I executed the above example code and added the screenshot below.
This approach feels more mathematical. I usually prefer this when I’m working with numeric data directly, without converting to strings.
Method 3 – Use Logarithms (math module)
If you want a more mathematical solution, you can use the math.log10() function in Python.
import math
# Method 3: Using math.log10
num = 98765
# Find the number of digits
digits = int(math.log10(num))
# Divide to get the first digit
first_digit = num // (10 ** digits)
print("The first digit is:", first_digit)Output:
The first digit is: 9I executed the above example code and added the screenshot below.
This method is efficient for very large numbers, especially when working with datasets like population counts or transaction IDs.
Method 4 – Use Recursion
Sometimes, I like to solve problems recursively. Here’s how you can do it:
# Method 4: Using recursion
def get_first_digit(num):
if num < 10:
return num
return get_first_digit(num // 10)
num = 98765
print("The first digit is:", get_first_digit(num))Output:
The first digit is: 9This method isn’t always the most efficient, but it’s a fun way to practice recursion.
Handle Negative Numbers
All the above methods work with positive integers. But what if your number is negative?
Here’s a quick fix:
num = -98765
# Convert to positive before applying methods
first_digit = int(str(abs(num))[0])
print("The first digit is:", first_digit)Output:
The first digit is: 9I often encounter this when working with financial data in the U.S., where negative numbers represent expenses or losses.
Handle Floating-Point Numbers
If you’re working with decimal numbers, you can still extract the first digit.
num = 123.456
first_digit = int(str(num)[0])
print("The first digit is:", first_digit)Output:
The first digit is: 1For floats, the string method is usually the simplest.
Which Method Should You Use?
- String slicing → Best for quick and easy solutions.
- While loop → Best when working with integers in pure math operations.
- Logarithms → Best for very large numbers.
- Recursion → Best for learning or practicing recursion.
In my projects, I usually go with string slicing unless performance is critical.
Obtaining the first digit of a number in Python is simple once you are familiar with the various approaches. Each method has its own advantages, and the one you choose depends on your use case.
Other Python tutorials you may also like:
- Compare Two Lists in Python and Return Non-Matching Elements
- Python Program to Check Whether a List Contains a Sublist
- Write List To CSV Python
- Split a List in Python By Comma
I am Bijay Kumar, a Microsoft MVP in SharePoint. Apart from SharePoint, I started working on Python, Machine learning, and artificial intelligence for the last 5 years. During this time I got expertise in various Python libraries also like Tkinter, Pandas, NumPy, Turtle, Django, Matplotlib, Tensorflow, Scipy, Scikit-Learn, etc… for various clients in the United States, Canada, the United Kingdom, Australia, New Zealand, etc. Check out my profile.
