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How To Convert a NumPy Array to List in Python

Published on August 3, 2022 · Updated on September 23, 2022
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By Pankaj
Developer and author at DigitalOcean.
How To Convert a NumPy Array to List in Python

Introduction

With NumPy, np.array objects can be converted to a list with the tolist() function. The tolist() function doesn’t accept any arguments. If the array is one-dimensional, a list with the array elements is returned. For a multi-dimensional array, a nested list is returned.

Prerequisites

In order to complete this tutorial, you will need:

This tutorial was tested with Python 3.9.6 and NumPy 1.23.3.

Converting one-dimensional NumPy Array to List

Let’s construct a one-dimensional array of [1, 2, 3]:

import numpy as np

# 1d array to list
arr_1 = np.array([1, 2, 3])

print(f'NumPy Array:\n{arr_1}')

This code will output:

NumPy Array:
[1 2 3]

Now, let’s use tolist():

import numpy as np

# 1d array to list
arr_1 = np.array([1, 2, 3])

print(f'NumPy Array:\n{arr_1}')

list_1 = arr_1.tolist()

print(f'List: {list_1}')

This new code will output:

List: [1, 2, 3]

The array has been converted from numpy scalars to Python scalars.

Converting multi-dimensional NumPy Array to List

Let’s construct a multi-dimensional array of [ [1, 2, 3], [4, 5, 6] ]:

import numpy as np

# 2d array to list
arr_2 = np.array([[1, 2, 3], [4, 5, 6]])

print(f'NumPy Array:\n{arr_2}')

This code will output:

NumPy Array:
[[1 2 3]
 [4 5 6]]

Now, let’s use tolist():

import numpy as np

# 2d array to list
arr_2 = np.array([[1, 2, 3], [4, 5, 6]])

print(f'NumPy Array:\n{arr_2}')

list_2 = arr_2.tolist()

print(f'List: {list_2}')

This new code will output:

List: [[1, 2, 3], [4, 5, 6]]

The array has been converted from numpy scalars to Python scalars.

Conclusion

In this article, you learned how to use tolist() to convert np.array objects to lists. It is applicable to one-dimensional and multi-dimensional arrays.

References

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About the authors
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Pankaj

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Developer and author at DigitalOcean.

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JournalDev
DigitalOcean Employee
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August 7, 2020

thanks for your help man , great buddy . actualluy i was working in opencv2 and the value was in array and i cant turn it until i found that it was a numpy array . hahahahahah

- akshit

    JournalDev
    DigitalOcean Employee
    DigitalOcean Employee badge
    July 22, 2020

    Thank you for this i can convert ndarray to list obj

    - arnaldo

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