When working with float values (numbers with decimal values) in our Python program, we might want to round them up or down, or to the nearest whole number.

In this article, we'll see some built-in functionalities that let us round numbers in Python. And we'll see how to use them with some examples.

We'll start with the round() function. By default, it rounds a number to the nearest whole number. We'll also see how to use the function's parameters to change the type of result returned to us.

We'll then talk about the math.ceil() and math.floor() methods which rounds up and rounds down a number to the nearest whole number/integer respectively. These two methods are from the built-in math module in Python.

How to Use the round() Function to Round to the Nearest Whole Number

The round() function takes in two parameters. Here's what the syntax looks like:

round(number, decimal_digits)

The first parameter – number – is the number we are rounding to the nearest whole number.

The second parameter – decimal_digits – is the number of decimals to be returned. The default value is 0.

Let's see some examples. 

x = 2.56789

print(round(x))
# 3

In our first example, we're using only one parameter – the number to be rounded, which is 2.56789.

When we passed in the number variable to the round() function, it got rounded to the nearest whole number which is 3.

That's how easy it is to use!

Now, let's work with the second parameter. 

x = 2.56789

print(round(x, 2))
# 2.57

The code above is similar to the last example except for the second parameter.  We passed in a value of two. This will round the number to the nearest hundredth (two decimal places).

In our case, 2.57 was returned. That is, 2.56789 to 2.57.

Let's see one last example to fully understand how the second parameter works. 

x = 2.56789

print(round(x, 3))
# 2.568

Now, we've made the second parameter 3. We'll get the number rounded to the nearest thousandth (three decimal places).

The initial number – 2.56789 – was rounded to 2.568.

How to Use the math.ceil() Method to Round Up a Number to the Nearest Whole Number

The math.ceil() method simple takes in the number to be rounded up as its parameter. Here's what the syntax looks like:

math.ceil(number)

Here's an example:

import math

x = 5.57468465

print(math.ceil(x))
# 6

In the code above, you'll notice that we first imported the math module: import math. This give us access to all the methods provided by the module.

We created an x variable which has 5.57468465 as its value.

In order to round this number up to the nearest whole number, we passed in the number (in the x variable) to the math.ceil() method: math.ceil(x).

The resulting value from this operation, as can be seen in the code above, is 6.

How to Use the math.floor() Method to Round Down a Number to the Nearest Whole Number

Just like we did in the last section, in order to use the math.floor() method, we must first import the math module.

Here's the syntax for math.floor() method:

math.floor(number)

Let's see an example. 

import math

x = 5.57468465

print(math.floor(x))
# 5

As expected, we passed in the number to be rounded down to the math.floor() method: math.floor(x). The x variable has the number 5.57468465 stored in it.

This number got rounded down to 5.

Conclusion

In this article, we talked about three built-in functionalities in Python that let us round numbers.

The round() function rounds a number to the nearest whole number.

The math.ceil() method rounds a number up to the nearest whole number while the math.floor() method rounds a number down to the nearest whole number. These two methods are both accessible through the math module.

With the examples given in each section, we were able to see how to use each functionality to obtain our desired result.

Happy coding!