# How to Append to Numpy Array

Numpy append() function merges two arrays and returns a new array, and the original array remains unchanged.

## Append to numpy array

To append elements to a numpy array in Python, use the np.append() method. The np.append() is a numpy library function that appends values to the end of an array.

### Syntax

``numpy.append(array, values, axis = None)``

### Parameters

The np.append() function takes three arguments.

1. array: It is an input array.
2. values: To be appended to the array.
3. axis: The axis along which the append operation is to be done.

### Return value

The np.append() function returns a copy of the array with values appended to the axis.

### Example

``````import numpy as np

array_one = np.arange(4)
print("First array : ", array_one)
print("Shape : ", array_one.shape)

array_two = np.arange(7, 11)
print("\nSecond array : ", array_two)
print("Shape : ", array_two.shape)

array_final = np.append(array_one, array_two)
print("\nFinal Array : ", array_final)``````

#### Output

``````First array : [0 1 2 3]
Shape : (4,)

Second array : [ 7 8 9 10]
Shape : (4,)

Final Array : [ 0 1 2 3 7 8 9 10]``````

We appended the second array to the first one and returned the new one with combined values.

## ValueError: all the input arrays must have same number of dimensions

The ValueError: all the input arrays must have same number of dimensions error occurs when you are trying to append an array to a different shape of the array. Both arrays should have the same shape.

``````import numpy as np

array_one = np.array([[21, 30],[19, 46]])
array_two = np.array([8, 9, 10, 11, 12])

final_array = np.append(array_one, array_two, axis=0)
print(final_array)``````

#### Output

``ValueError: all the input arrays must have same number of dimensions, but the array at index 0 has 2 dimension(s) and the array at index 1 has 1 dimension(s)``

And we are getting the ValueError because the input arrays did not have the same number of dimensions.

That’s it.

## Related posts

np.concatenate

How to create empty numpy array

How to copy an array

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