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 listtest_list = [4, 5, 2, 6, 7, 8, 10]# printing original listprint("The original list : " + str(test_list))# initializing NN = 5# using list slicing# Get last N elements from listres = test_list[-N:]# print resultprint("The last N elements of list are : " + str(res)) |
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 listtest_list = [4, 5, 2, 6, 7, 8, 10]# printing original listprint("The original list : " + str(test_list))# initializing NN = 5# using islice() + reversed()# Get last N elements from listres = list(islice(reversed(test_list), 0, N))res.reverse()# print resultprint("The last N elements of list are : " + str(res)) |
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 listtest_list = [4, 5, 2, 6, 7, 8, 10]# printing original listprint("The original list : " + str(test_list))# initializing NN = 5# Get last N elements from listx=test_list[::-1]res=[]i=0while(i<N): res.append(x[i]) i+=1res.reverse()# print resultprint("The last N elements of list are : " + str(res)) |
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 listdef get_last_n(lst, n): yield lst[len(lst)-n:len(lst)]# initializing listtest_list = [4, 5, 2, 6, 7, 8, 10]# printing original listprint("The original list : " + str(test_list))# print resultprint("The last N elements of list are : " + str(list(get_last_n(test_list, 5))))#This code is contributed by Edula Vinay Kumar Reddy |
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)
