NumPy - insert() function

The NumPy insert() function inserts values along the given axis before the given indices.

Syntax

numpy.insert(arr, obj, values, axis=None)

Parameters

`arr`	`Required.` Specify the input array (array_like).
`obj`	`Required.` Specify object that defines the index or indices before which values is inserted. It can be int, slice or sequence of ints.
`values`	`Required.` Specify values to insert into arr. If the type of values is different from that of arr, values is converted to the type of arr.
`axis`	`Optional.` Specify the axis along which to insert values. If axis is None then arr is flattened first.

Return Value

Returns a copy of arr with values inserted.

Example:

In the example below, insert() function is used to insert a scalar value at given index.

import numpy as np

Arr = np.array([[10, 20],
                [30, 40]])

#inserting 5 in the array with axis=None
Arr1 = np.insert(Arr, 1, 5)

#inserting 5 in the array with axis=0
Arr2 = np.insert(Arr, 1, 5, axis=0)

#inserting 5 in the array with axis=1
Arr3 = np.insert(Arr, 1, 5, axis=1)

#displaying results
print("Arr is:")
print(Arr)
print("\nArr1 is (insert with axis=None):")
print(Arr1)
print("\nArr2 is (insert with axis=0):")
print(Arr2)
print("\nArr3 is (insert with axis=1):")
print(Arr3)

The output of the above code will be:

Arr is:
[[10 20]
 [30 40]]

Arr1 is (insert with axis=None):
[10  5 20 30 40]

Arr2 is (insert with axis=0):
[[10 20]
 [ 5  5]
 [30 40]]

Arr3 is (insert with axis=1):
[[10  5 20]
 [30  5 40]]

Example:

In the example below, insert() function is used to insert a list at given index.

import numpy as np

Arr = np.array([[10, 20],
                [30, 40]])

#inserting list with axis=0
Arr1 = np.insert(Arr, 1, [100, 200], axis=0)

#inserting list with axis=1
Arr2 = np.insert(Arr, 1, [100, 200], axis=1)

#displaying results
print("Arr is:")
print(Arr)
print("\nArr1 is (insert with axis=0):")
print(Arr1)
print("\nArr2 is (insert with axis=1):")
print(Arr2)

The output of the above code will be:

Arr is:
[[10 20]
 [30 40]]

Arr1 is (insert with axis=0):
[[ 10  20]
 [100 200]
 [ 30  40]]

Arr2 is (insert with axis=1):
[[ 10 100  20]
 [ 30 200  40]]

Example:

A list can be inserted at multiple indices of an array. Consider the example below:

import numpy as np

Arr = np.array([[10, 20, 30],
                [40, 50, 60],
                [70, 80, 90]])

list1 = [1, 2, 3]
list2 = [[1], [2], [3]]
#inserting list with axis=0
Arr1 = np.insert(Arr, [1, 2], list1, axis=0)

#inserting list with axis=1
Arr2 = np.insert(Arr, [1, 2], list2, axis=1)

#displaying results
print("Arr is:")
print(Arr)
print("\nArr1 is (insert with axis=0):")
print(Arr1)
print("\nArr2 is (insert with axis=1):")
print(Arr2)

The output of the above code will be:

Arr is:
[[10 20 30]
 [40 50 60]
 [70 80 90]]

Arr1 is (insert with axis=0):
[[10 20 30]
 [ 1  2  3]
 [40 50 60]
 [ 1  2  3]
 [70 80 90]]

Arr2 is (insert with axis=1):
[[10  1 20  1 30]
 [40  2 50  2 60]
 [70  3 80  3 90]]

❮ NumPy - Array Manipulation