Python:NumPy .append()

The .append() function adds values to the end of an array and returns a ndarray with the values appended.

Syntax

numpy.append(array, values, axis)

Where array is the array being appended to. The values parameter is another array specifying the values to add to array. If axis is specified, values must be the same shape as array without that axis. If axis is not specified, values can be any shape, and both array and values will be flattened before the values are appended. The axis value specifies the axis along which values are appended.

Example

The example below creates two ndarrays and appends one to the other.

import numpy as np

nd1 = np.array([[1,2,3],[4,5,6]])
nd2 = np.array([[7,8,9]])

print(nd1)
print(nd2)
print(np.append(nd1,nd2,0))

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This produces the following output:

[[1 2 3]
 [4 5 6]]

[[7 8 9]]

[[1 2 3]
 [4 5 6]
 [7 8 9]]

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Codebyte Example

The following example creates two arrays and demonstrates appending them using .append(), both without specifying an axis (resulting in a 1D array) and along specified axes (rows and columns):

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