How To Get The Decimal Part Of A Number In Python?

In this tutorial, I will explain how to get the decimal part of a number in Python. As a Python developer, I recently faced this issue while developing a financial application for a client in New York City, and I found several effective methods to handle this task. Let’s get into the details.

Table of Contents

Methods to Extract the Decimal Part of a Number in Python

Python offers several ways to extract the decimal part of a number. Here, I’ll cover the most common methods:

Method 1. Use the Modulo Operator

The modulo operator (%) is a simple and effective way to extract the decimal part of a float. Here’s how you can do it:

def get_decimal_part(number):
    return number % 1

# Example
number = 123.456
decimal_part = get_decimal_part(number)
print(f"The decimal part of {number} is {decimal_part}")

Output:

The decimal part of 123.456 is 0.45600000000000307

I have executed the above example and added the screenshot below.

In this example, 123.456 % 1 returns 0.456 , which is the decimal part of the number.

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Method 2. Use the math.modf() Function

The math.modf() function splits a floating-point number into its integer and fractional parts. This function is part of Python’s standard library.

import math

def get_decimal_part(number):
    fractional, integer = math.modf(number)
    return fractional

# Example
number = 789.123
decimal_part = get_decimal_part(number)
print(f"The decimal part of {number} is {decimal_part}")

Output:

The decimal part of 789.123 is 0.1230000000000473

I have executed the above example and added the screenshot below.

Get the Decimal Part of a Number in Python

In this example, math.modf(789.123) returns (0.123, 789.0), where 0.123 is the fractional part.

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Method 3. Use String Manipulation

Another method involves converting the number to a string and then manipulating the string to extract the decimal part.

def get_decimal_part(number):
    str_number = str(number)
    if '.' in str_number:
        return '0.' + str_number.split('.')[1]
    else:
        return '0.0'

# Example
number = 456.789
decimal_part = get_decimal_part(number)
print(f"The decimal part of {number} is {decimal_part}")

Output:

The decimal part of 456.789 is 0.789

I have executed the above example and added the screenshot below.

How to Get the Decimal Part of a Number in Python

In this example, the number is converted to a string, split at the decimal point, and the fractional part is reconstructed as a string.

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Method 4. Use the Decimal Module

Python’s decimal module provides support for fast and correctly-rounded decimal floating point arithmetic. This method is particularly useful for financial applications.

from decimal import Decimal

def get_decimal_part(number):
    decimal_number = Decimal(str(number))
    return decimal_number - int(decimal_number)

# Example
number = 123.456
decimal_part = get_decimal_part(number)
print(f"The decimal part of {number} is {decimal_part}")

In this example, Decimal(str(number)) ensures that the number is treated with high precision, and subtracting the integer part gives the fractional part.

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Examples

Let’s see some real-world examples where extracting the decimal part is necessary.

1. Financial Application: Calculate Change

Imagine you’re developing a point-of-sale system for a retail store in Los Angeles. You need to calculate the change to be given to the customer, and you want to display the cents separately.

def calculate_change(total_amount, payment):
    change = payment - total_amount
    cents = get_decimal_part(change)
    return change, cents

# Example
total_amount = 19.95
payment = 20.00
change, cents = calculate_change(total_amount, payment)
print(f"Total change: ${change:.2f}, Cents: {cents:.2f}")

In this example, the get_decimal_part function helps isolate the cents from the total change.

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2. Scientific Data Analysis: Precision Measurements

Suppose you’re working on a scientific project in a lab in Houston, and you need to record the fractional part of measurements precisely.

measurements = [1.234, 2.345, 3.456, 4.567]
fractional_parts = [get_decimal_part(m) for m in measurements]
print(f"Fractional parts of measurements: {fractional_parts}")

This example shows how to extract the fractional parts of a list of measurements.

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Conclusion

In this tutorial, I have explained how to get the decimal part of a number in Python. I discussed several methods to achieve this task, using the modulo operator, using math.modf() function, using string manipulation and using a decimal module. We also discussed real-time examples of financial application and scientific data analysis.