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In this chapter, we will discuss about NumPy – append. This function adds values at the end of an input array. The append operation is not in place, a new array is allocated. Also, the dimensions of the input arrays must match otherwise ValueError will be generated.

The function takes the following parameters.

numpy.append(arr, values, axis)

Where,

Sr.No.	Parameter & Description
1	arrInput array
2	values to be appended to arr. It must be of the same shape as of arr (excluding axis of appending)
3	axisThe axis along which append operation is to be done. If not given, both parameters are flattened

Example Of NumPy append

import numpy as np 
a = np.array([[1,2,3],[4,5,6]]) 

print 'First array:' 
print a 
print '\n'  

print 'Append elements to array:' 
print np.append(a, [7,8,9]) 
print '\n'  

print 'Append elements along axis 0:' 
print np.append(a, [[7,8,9]],axis = 0) 
print '\n'  

print 'Append elements along axis 1:' 
print np.append(a, [[5,5,5],[7,8,9]],axis = 1)

Its output would be as follows −

First array:
[[1 2 3]
 [4 5 6]]

Append elements to array:
[1 2 3 4 5 6 7 8 9]

Append elements along axis 0:
[[1 2 3]
 [4 5 6]
 [7 8 9]]

Append elements along axis 1:
[[1 2 3 5 5 5]
 [4 5 6 7 8 9]]