NumPy tolist()

import numpy as np

array1 = np.array([[0, 1], [2, 3]])

# convert a NumPy array to Python list
list1 = array1.tolist()

print(list1, type(list1))

# Output : [[0, 1], [2, 3]] <class 'list'>

tolist() Syntax

The syntax of tolist() is:

ndarray.tolist()

tolist() Arguments

The tolist() method takes no arguments.

tolist() Return Value

The tolist() method returns a Python list.

Example 1: Convert a Multidimensional Array

The tolist() method converts a multidimensional array into a nested list.

import numpy as np

array1 = np.array([[[0, 1], [2, 3]], [[4, 5], [6, 7]]])

# convert the array to list
list1 = array1.tolist()

print(list1)

Output

[[[0, 1], [2, 3]], [[4, 5], [6, 7]]]

Difference Between tolist() and list()

The key differences between tolist() and list() are

• The tolist() method converts a multidimensional array into a nested list whereas list() converts it to a list of arrays. For example,

import numpy as np

# create a 2-D array
array1 = np.array([[1, 2], [3, 4]])

# convert a 2-D array to nested list
list1 = array1.tolist()

# convert a 2-D array to a list of arrays
list2 = list(array1)

print('Using array.tolist(): ', list1)
print('Using list(array): ', list2)

Output

Using array.tolist():  [[1, 2], [3, 4]]
Using list(array):  [array([1, 2]), array([3, 4])]

• tolist() changes NumPy data types to Python data types, but list() doesn't.

import numpy as np

# create a numpy array
array1 = np.array([1, 2])

# convert an array to a list using tolist()
list1 = array1.tolist()

# convert an array to a list using list()
list2 = list(array1)

print("Datatype of original array:", type(array1[0]))
print("Datatype after using array.tolist():", type(list1[0]))
print("Datatype after using array.tolist():", type(list2[0]))

Output

Datatype of original array: <class 'numpy.int64'>
Datatype after using array.tolist(): <class 'int'>
Datatype after using array.tolist(): <class 'numpy.int64'>

• tolist() works with 0d numpy arrays, but list() doesn't.

import numpy as np

# create a list of arrays
array1 = np.array(123)

# convert an array to a list using tolist()
list1 = array1.tolist()
print(list1) #123

# convert an array to a list using list()
list2 = list(array1)  #TypeError: iteration over a 0-d array
print(list2)

Output

123
TypeError: iteration over a 0-d array