Solved: rounding numbers to n digits

Rounding numbers is a common task in various mathematical computations, data analysis, and presentation of results to make them more readable and easily understandable. In Python, there are different ways to round numbers to a specific number of digits. In this article, we will discuss one such solution using the round function and dive deeper into the process, understanding the code step-by-step. Additionally, we will explore other functions and libraries that play a crucial role in addressing similar problems.


Rounding a number means approximating it to its nearest value, usually at a specific decimal place. For example, rounding the number 3.14159 to 2 decimal places gives us 3.14. In Python, the built-in function round() is used to round numbers to a specified number of digits.

Solution to the problem

To round a number to n decimal places, you can use the round() function in Python in the following way:

number_to_round = 3.14159
rounded_number = round(number_to_round, 2)
print(rounded_number)  # Output: 3.14

In this example, we’ve rounded the number 3.14159 to 2 decimal places, resulting in 3.14.

Step-by-step explanation of the code

1. Define the number you want to round (number_to_round).
2. Use the round() function to round the number to the desired decimal places (n) by passing the number and the number of decimal places as arguments.
3. Save the result as a variable (rounded_number).
4. Print the result to verify the output.

Now, let’s dive deeper into some of the functions and libraries related to this problem.

The round() Function

The round() function is a built-in Python function that returns a floating-point number rounded to a specified number of decimal places. The function takes two arguments – the number to be rounded and the number of decimal places to round to.

The first argument is the number that needs to be rounded, and the second is optional, indicating the number of decimal places to be rounded. If the second argument is not provided, the function rounds the number to the nearest integer.

The round() function applies round half to even rounding, also known as banker’s rounding, which rounds to the nearest even number when the number to be rounded is exactly halfway between two possible rounded values.

Other Libraries and Functions for Rounding Numbers in Python

    • math library: The math library in Python provides a wide range of mathematical functions and operations. Some of the rounding-related functions in this library include ceil() and floor(). The ceil() function rounds a number up, whereas the floor() function rounds it down.
    • Decimal library: The Decimal library provides an alternative rounding method, avoiding some issues with floating-point representation constraints. It offers precise control over the rounding process using functions like quantize() and round() and is particularly useful in financial computations or when you need exact control over rounding.

In summary, rounding numbers in Python can be done using the built-in round() function. Additionally, other functions and libraries such as math and Decimal can provide alternative methods or greater control over the rounding process, depending on the specific context and requirements of your problem.

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