NumPy: insert() function

Last update on May 28 2022 11:18:11 (UTC/GMT +8 hours)

numpy.insert() function

The insert() function is used to insert values along the given axis before the given indices.

Syntax:

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

Version: 1.15.0

Parameter:

Name	Description	Required / Optional
arr	Input array.	Required
obj	Object that defines the index or indices before which values is inserted. Support for multiple insertions when obj is a single scalar or a sequence with one element (similar to calling insert multiple times).	Required
values	[array_like] Values to insert into arr. If the type of values is different from that of arr, values is converted to the type of arr. values should be shaped so that arr[...,obj,.. .] = values is legal	Optional
axis	Axis along which to insert values. If axis is None then arr is flattened first.	Optional

Return value:

out [ndarray] A copy of arr with values inserted. Note that insert does not occur in-place: a new array is returned. If axis is None, out is a flattened array.

Example-1: numpy.insert()

>>> import numpy as np
>>> x = np.array([[0,0], [1,1], [2,2]])
>>> x
array([[0, 0],
       [1, 1],
       [2, 2]])
>>> np.insert(x, 2, 4)
array([0, 0, 4, 1, 1, 2, 2])
>>> np.insert(x, 2, 4, axis=1)
array([[0, 0, 4],
       [1, 1, 4],
       [2, 2, 4]])

Pictorial Presentation:

Example-2: numpy.insert()

>>> import numpy as np
>>> x = np.array([[0,0], [1,1], [2,2]])
>>> np.insert(x, [1], [[3], [4], [5]], axis=1) 
array([[0, 3, 0],
       [1, 4, 1],
       [2, 5, 2]])
>>> np.array_equal(np.insert(x, 1, [3, 4, 5], axis=1), np.insert(x, [1], [[3], [4], [5]], axis=1))
True

Pictorial Presentation:

Example-3: numpy.insert()

>>> import numpy as np
>>> x = np.array([[0,0], [1,1], [2,2]])
>>> y = x.flatten()
>>> y
array([0, 0, 1, 1, 2, 2])
>>> np.insert(y, [3,3], [6,7])
array([0, 0, 1, 6, 7, 1, 2, 2])
>>> np.insert(y, slice(3,5),[7,8])
array([0, 0, 1, 7, 1, 8, 2, 2])
>>> np.insert(y, [3,3], [8.12, False])
array([0, 0, 1, 8, 0, 1, 2, 2])

Example-4: numpy.insert()


>>> import numpy as np
>>> z = np.arange(12).reshape(3,4)
>>> idz = (1, 3)
>>> np.insert(z, idz, 777, axis=1)
array([[  0, 777,   1,   2, 777,   3],
       [  4, 777,   5,   6, 777,   7],
       [  8, 777,   9,  10, 777,  11]])

Pictorial Presentation:

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