Python | Calculate difference between adjacent elements in given list

Given a list, the task is to create a new list containing difference of adjacent elements in the given list. 

Method #1: Using zip()

Python3

# Python code to demonstrate
# to calculate difference
# between adjacent elements in list


# initialising _list
ini_list = [5, 4, 89, 12, 32, 45]

# printing iniial_list
print("intial_list", str(ini_list))

# Calculating difference list
diff_list = []
for x, y in zip(ini_list[0::], ini_list[1::]):
    diff_list.append(y-x)

# printing difference list
print ("difference list: ", str(diff_list))

Output:

intial_list [5, 4, 89, 12, 32, 45]
difference list:  [-1, 85, -77, 20, 13]

Time Complexity: O(n), where n is the length of the list ini_list 
Auxiliary Space: O(n) additional space of size n is created where n is the number of elements in the diff list 

Method #2: Using Naive approach

Python3

# Python code to demonstrate
# to calculate difference
# between adjacent elements in list


# initialising _list
ini_list = [5, 4, 89, 12, 32, 45]

# printing iniial_list
print("intial_list", str(ini_list))

# Calculating difference list
diff_list = []

for i in range(1, len(ini_list)):
    diff_list.append(ini_list[i] - ini_list[i-1])

# printing difference list
print ("difference list: ", str(diff_list))

Output:

intial_list [5, 4, 89, 12, 32, 45]
difference list:  [-1, 85, -77, 20, 13]

Method #3: Using numpy

Python3

# Python code to demonstrate
# to calculate difference
# between adjacent elements in list

import numpy as np
# initialising _list
ini_list = np.array([5, 4, 89, 12, 32, 45])

# printing iniial_list
print("intial_list", str(ini_list))

# Calculating difference list
diff_list = np.diff(ini_list)

# printing difference list
print ("difference list: ", str(diff_list))

Output:

intial_list [ 5  4 89 12 32 45]
difference list:  [ -1  85 -77  20  13]

 Method #4: Using list comprehension(one liner)

To calculate the difference between adjacent elements in a list using list comprehension, you can use the following approach:

Python3

# initializing the list
ini_list = [5, 4, 89, 12, 32, 45]

# using list comprehension to calculate the difference between adjacent elements
diff_list = [ini_list[i+1] - ini_list[i] for i in range(len(ini_list)-1)]

# printing the difference list
print(diff_list)
#This code is contributed by Edula Vinay Kumar Reddy

Output

[-1, 85, -77, 20, 13]

Time complexity: O(n)

Auxiliary Space: O(n)

Using map and lambda:

Approach:

lst[:-1] returns [5, 4, 89, 12, 32], which is lst with the last element removed.
lst[1:] returns [4, 89, 12, 32, 45], which is lst with the first element removed.
The lambda x, y: y – x function takes two arguments x and y and returns their difference y – x.
map(lambda x, y: y – x, lst[:-1], lst[1:]) applies the lambda function to corresponding elements from lst[:-1] and lst[1:], resulting in an iterator object of the form <map object at 0x…>.
list(map(lambda x, y: y – x, lst[:-1], lst[1:])) converts the iterator object to a list, which is the output of diff_adjacent_elements_3.
The resulting list is [-1, 85, -77, 20, 13], which is the difference between adjacent elements in the input list [5, 4, 89, 12, 32, 45].

Python3

def diff_adjacent_elements_3(lst):
    return list(map(lambda x, y: y - x, lst[:-1], lst[1:]))

initial_list = [5, 4, 89, 12, 32, 45]
diff_list = diff_adjacent_elements_3(initial_list)

print(f"Input list: {initial_list}")
print(f"Difference list: {diff_list}")

Output

Input list: [5, 4, 89, 12, 32, 45]
Difference list: [-1, 85, -77, 20, 13]

Time Complexity: O(n)
Auxiliary Space: O(n)