# Find Difference Between Numbers In Array Using np.diff — pythonpip.com

This tutorial help to find the differences between numbers in an array by `np.diff()`

method. You can compare two or more array using this method.

# Python np.diff()

The **NumPy** array method `np.diff()`

finds the differences between numbers in an array. The `np.diff()`

function can be used to compare two or more arrays. If only one array is provided, the difference is calculated using `res[i] = arr[i+1] - arr[i]`

.

# Syntax

`numpy.diff(a, n = 1, axis= -1, prepend = < no value >, append = < no value >)`

# Arguments

**a**: This is the source array for which the difference is found using the`np.diff()`

function.**n**: The number of times the array is differenced is passed as the argument to`n`

. This is by default set to**1**.**axis**: It is used to calculate the difference. It signifies that left to right is from right to left. The value is set to -1 by default. The axis can, however, be set to**0**.**prepend**: The values appended at the beginning before performing the diff() function.**append**: The values that are appended at the ending before performing the diff() function.

# Return Value

The function **np.diff()** returns an array. This array contains values that represent the difference between two array integers.

Let’s takes some examples to understand **np.diff()** method fucntionality:

# Finding the difference in a single array using np.diff()

import numpy as np

arr = np.array([12, 10, 45, 65, 3])

diff_arr = np.diff(arr)

print(diff_arr)

## Output:

`[ -2 35 20 -62] ** Process exited - Return Code: 0 ** Press Enter to exit terminal`

We have imported **numpy** packages at the top of the file, created a new array and passed this array to `np.diff()`

function.

The formula to calculate array number difference:

`diff_arr[i] = arr[i+1] - arr[i]`

As we can see the first index of the output array is store **-2**, that the difference between two array number( **10–12**).

**The outpot have :**

`-2 = 10-12 35 = 45-10 20 = 65-45 -62 = 3-65`

# Finding the difference in a Multiple array using np.diff()

We’ll subtract the first array elements from the second array elements.

`# Importing numpy as np import numpy as np # array arr = np.array([[12, 10, 45, 65, 3], [45, 16, 35, 25, 83]]) # creating a new array diff_arr = np.diff(arr, n=1, axis=0) print(diff_arr)`

**Output:**

`[[ 33 6 -10 -40 80]] ** Process exited - Return Code: 0 ** Press Enter to exit terminal`

We have imported NumPy packages at the top of the file, created two new arrays and passed this array to `np.diff()`

function.

The formula to calculate array number difference:

`diff_arr[0][i] = arr[1][i]-arr[0][i]`

As we can see the first index of the output array is store -2, which is the difference between two array number ( **10–12**).

The output has:

`33 = 45-12 ... ...`

*Originally published at **https://www.pythonpip.com** on May 16, 2022.*