Python | Get last N elements from given list

Accessing elements in a list has many types and variations. These are an essential part of Python programming and one must have the knowledge to perform the same. This article discusses ways to fetch the last N elements of list. Let’s discuss certain solution to perform this task.
Method #1 : Using list slicing
This problem can be performed in 1 line rather than using a loop using the list slicing functionality provided by Python. Minus operator specifies slicing to be done from rear end.

Python3

# Python3 code to demonstrate
# Get last N elements from list
# using list slicing

# initializing list
test_list = [4, 5, 2, 6, 7, 8, 10]

# printing original list
print("The original list : " + str(test_list))

# initializing N
N = 5

# using list slicing
# Get last N elements from list
res = test_list[-N:]

# print result
print("The last N elements of list are : " + str(res))

Output : 

The original list : [4, 5, 2, 6, 7, 8, 10]
The last N elements of list are : [2, 6, 7, 8, 10]

Time Complexity: O(n) where m and n is the number of elements in the list. list slicing performs n number of operations.
Auxiliary Space: O(n), extra space is required where n is the number of elements in the list

Method #2 : Using islice() + reversed()
The inbuilt functions can also be used to perform this particular task. The islice function can be used to get the sliced list and reversed function is used to get the elements from rear end.

Python3

# Python3 code to demonstrate
# Get last N elements from list
# using islice() + reversed()
from itertools import islice

# initializing list
test_list = [4, 5, 2, 6, 7, 8, 10]

# printing original list
print("The original list : " + str(test_list))

# initializing N
N = 5

# using islice() + reversed()
# Get last N elements from list
res = list(islice(reversed(test_list), 0, N))
res.reverse()

# print result
print("The last N elements of list are : " + str(res))

Output : 

The original list : [4, 5, 2, 6, 7, 8, 10]
The last N elements of list are : [2, 6, 7, 8, 10]

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

Method #3 : Using loop

Python3

# Python3 code to demonstrate
# Get last N elements from list

# initializing list
test_list = [4, 5, 2, 6, 7, 8, 10]

# printing original list
print("The original list : " + str(test_list))

# initializing N
N = 5


# Get last N elements from list
x=test_list[::-1]
res=[]
i=0
while(i<N):
    res.append(x[i])
    i+=1
res.reverse()
# print result
print("The last N elements of list are : " + str(res))

Output

The original list : [4, 5, 2, 6, 7, 8, 10]
The last N elements of list are : [2, 6, 7, 8, 10]

Time Complexity : O(N)

Auxiliary Space : O(1)

Method #4: Using a generator function

You can define a generator function that yields the last N elements of a list.

Python3

# Python3 code to demonstrate
# Get last N elements from list
def get_last_n(lst, n):
    yield lst[len(lst)-n:len(lst)]

# initializing list
test_list = [4, 5, 2, 6, 7, 8, 10]
# printing original list
print("The original list : " + str(test_list))

# print result
print("The last N elements of list are : " + str(list(get_last_n(test_list, 5))))
#This code is contributed by Edula Vinay Kumar Reddy

Output

The original list : [4, 5, 2, 6, 7, 8, 10]
The last N elements of list are : [[2, 6, 7, 8, 10]]

Time Complexity : O(N)

Auxiliary Space : O(1)