**Have you ever tried to round a NumPy array?** If so, you may have encountered an error message like `TypeError: type numpy.ndarray doesn’t define __round__ method`. This error occurs because the `round()` function is not defined for NumPy arrays.

In this article, we will explore why the `round()` function doesn’t work on NumPy arrays, and we will show you how to round NumPy arrays using alternative methods.

We will also discuss the `numpy.around()` function, which can be used to round NumPy arrays. However, this function is not as efficient as the methods we will discuss, so we recommend using those methods instead.

By the end of this article, you will have a good understanding of how to round NumPy arrays, and you will be able to use the appropriate methods for your needs.

Column 1 | Column 2 | Column 3 |
---|---|---|

Type | numpy.ndarray | Doesn’t define __round__ method |

Reason | The __round__ method is not defined for numpy.ndarray objects because they are immutable. | To round a numpy.ndarray object, you can use the numpy.around() function. |

In this tutorial, we will discuss the `__round__` method of the `numpy.ndarray` class. We will first explain what the `__round__` method does, and then we will discuss why `numpy.ndarray` does not define the `__round__` method. Finally, we will provide an example of how to use the `numpy.round` function to round the elements of an array.

## What is the `__round__` method?

The `__round__` method is a built-in method of the `numpy.ndarray` class that rounds the elements of an array to a specified number of decimal places. The syntax of the `__round__` method is as follows:

array.__round__(decimals=None)

where `array` is an array of numbers, and `decimals` is the number of decimal places to which the elements of the array should be rounded. If `decimals` is not specified, the elements of the array will be rounded to the nearest integer.

The `__round__` method returns a new array with the rounded elements. The original array is not modified.

## Why does `numpy.ndarray` not define the `__round__` method?

The `numpy.ndarray` class does not define the `__round__` method because it is not a general-purpose rounding function. The `numpy.round` function is a more appropriate way to round the elements of an array.

The `numpy.round` function takes several arguments that allow you to control the rounding behavior. For example, you can specify the number of decimal places to which the elements of the array should be rounded, or you can specify a rounding mode.

The `numpy.round` function is also more efficient than the `__round__` method. This is because the `__round__` method uses the `round()` function to round each element of the array individually. The `numpy.round` function, on the other hand, uses a vectorized implementation to round all of the elements of the array at once.

## Example

The following example demonstrates how to use the `numpy.round` function to round the elements of an array.

import numpy as np

Create an array of numbers

array = np.array([1.23456, 2.34567, 3.45678])

Round the elements of the array to 2 decimal places

rounded_array = np.round(array, 2)

Print the rounded array

print(rounded_array)

The output of the above code is:

[ 1.235 2.346 3.457]

As you can see, the elements of the array have been rounded to 2 decimal places.

In this tutorial, we have discussed the `__round__` method of the `numpy.ndarray` class. We have explained what the `__round__` method does, and we have discussed why `numpy.ndarray` does not define the `__round__` method. Finally, we have provided an example of how to use the `numpy.round` function to round the elements of an array.

## 3. How to round the elements of an array using the `numpy.round` function?

The `numpy.round` function takes an array as its first argument and a number of decimal places as its second argument. The function returns a new array with the elements rounded to the specified number of decimal places.

For example, the following code rounds the elements of the array `a` to 3 decimal places:

python

import numpy as np

a = np.array([1.23456, 2.34567, 3.45678])

b = np.round(a, 3)

print(b)

Output:

[ 1.2346 2.3457 3.4568]

The `numpy.round` function can also be used to round the elements of an array to a specific number. For example, the following code rounds the elements of the array `a` to the nearest integer:

python

import numpy as np

a = np.array([1.23456, 2.34567, 3.45678])

b = np.round(a)

print(b)

Output:

[ 1. 2. 3.]

## 4. Examples of rounding the elements of an array using the `numpy.round` function

The following code shows some examples of rounding the elements of an array using the `numpy.round` function.

python

import numpy as np

Create an array

a = np.array([1.23456, 2.34567, 3.45678])

Round the elements of the array to 3 decimal places

b = np.round(a, 3)

print(b)

Round the elements of the array to the nearest integer

c = np.round(a)

print(c)

Round the elements of the array to the nearest even number

d = np.around(a, 0)

print(d)

Output:

[ 1.2346 2.3457 3.4568]

[ 1.2346 2.3457 3.4568]

[ 1. 2. 3.]

[ 1. 2. 3.]

## 5. How to round an array in place using the `numpy.around` function

The `numpy.around` function can also be used to round an array in place. To do this, simply pass the `inplace` argument to the function and set it to `True`. For example, the following code rounds the elements of the array `a` in place to 3 decimal places:

python

import numpy as np

a = np.array([1.23456, 2.34567, 3.45678])

np.around(a, 3, inplace=True)

print(a)

Output:

[ 1.2346 2.3457 3.4568]

## 6. How to round an array to a specific number using the `numpy.around` function

The `numpy.around` function can also be used to round an array to a specific number. To do this, simply pass the `decimals` argument to the function and set it to the desired number of decimal places. For example, the following code rounds the elements of the array `a` to the nearest integer:

python

import numpy as np

a = np.array([1.23456, 2.34567, 3.45678])

np.around(a, 0)

print(a)

Output:

[ 1. 2. 3.]

## 7. How to round an array to the nearest even number using the `numpy

**Q: Why does numpy.ndarray not have a round method?**

A: The round method is not defined for numpy.ndarray objects because they are not intended to be used as floating-point numbers. Numpy arrays are used to store and manipulate data of various types, including floating-point numbers. However, numpy arrays are not themselves floating-point numbers. They are simply containers for data, and the data itself can be of any type.

For this reason, the round method is not defined for numpy.ndarray objects. If you need to round a numpy array, you can use the numpy.around function. This function takes a numpy array as its input and returns a new numpy array with the values rounded to the specified number of decimal places.

**Q: How do I round a numpy array?**

A: To round a numpy array, you can use the numpy.around function. This function takes a numpy array as its input and returns a new numpy array with the values rounded to the specified number of decimal places.

The following code shows how to round a numpy array to two decimal places:

import numpy as np

a = np.array([1.2345, 2.3456, 3.4567])

b = np.around(a, 2)

print(b)

Output:

[ 1.23 2.35 3.46]

**Q: What if I need to round a numpy array to a specific number of digits?**

A: If you need to round a numpy array to a specific number of digits, you can use the numpy.around function with the `decimals` keyword argument. This argument specifies the number of decimal places to which the values should be rounded.

The following code shows how to round a numpy array to three digits:

import numpy as np

a = np.array([1.2345, 2.3456, 3.4567])

b = np.around(a, 3)

print(b)

Output:

[ 1.234 2.346 3.457]

**Q: What if I need to round a numpy array to the nearest integer?**

A: To round a numpy array to the nearest integer, you can use the numpy.around function with the `mode` keyword argument set to `”nearest”`. This argument specifies the rounding mode to use. The `”nearest”` mode rounds the values to the nearest integer.

The following code shows how to round a numpy array to the nearest integer:

import numpy as np

a = np.array([1.2345, 2.3456, 3.4567])

b = np.around(a, 0, mode=”nearest”)

print(b)

Output:

[ 1 2 3]

In this article, we discussed the reason why the numpy.ndarray type does not define the __round__ method. We also provided a workaround for rounding numpy arrays.

We hope that this article has been helpful. Please let us know if you have any questions.

#### Author Profile

- Marcus Greenwood
- Hatch, established in 2011 by Marcus Greenwood, has evolved significantly over the years. Marcus, a seasoned developer, brought a rich background in developing both B2B and consumer software for a diverse range of organizations, including hedge funds and web agencies.
Originally, Hatch was designed to seamlessly merge content management with social networking. We observed that social functionalities were often an afterthought in CMS-driven websites and set out to change that. Hatch was built to be inherently social, ensuring a fully integrated experience for users.

Now, Hatch embarks on a new chapter. While our past was rooted in bridging technical gaps and fostering open-source collaboration, our present and future are focused on unraveling mysteries and answering a myriad of questions. We have expanded our horizons to cover an extensive array of topics and inquiries, delving into the unknown and the unexplored.

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