The problem of finding a average values in a list is quite common. But sometimes this problem can be extended in two lists and hence becomes a modified problem. This article discusses shorthands by which this task can be performed easily. Let’s discuss certain ways in which this problem can be solved.
Method #1 : Using sum() + len() + “+” operator
The average value can be determined by the conventional sum() and len function of python and the extension of one to two lists can be dealt using the “+” operator.
Python3
# Python3 code to demonstrate# Average of two lists# using sum() + len() + "+" operator# initializing liststest_list1 = [1, 3, 4, 5, 2, 6]test_list2 = [3, 4, 8, 3, 10, 1]# printing the original listsprint ("The original list 1 is : " + str(test_list1))print ("The original list 2 is : " + str(test_list2))# Average of two lists# using sum() + len() + "+" operatorres = sum(test_list1 + test_list2) / len(test_list1 + test_list2)# printing resultprint ("The Average of both lists is : " + str(res)) |
The original list 1 is : [1, 3, 4, 5, 2, 6] The original list 2 is : [3, 4, 8, 3, 10, 1] The Average of both lists is : 4.166666666666667
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 res list
Method #2 : Using sum() + len() + chain()
Another method to perform this particular task is by using the chain function which performs the task similar to the “+” operator but using an iterator, hence faster.
Python3
# Python3 code to demonstrate# Average of two lists# using sum() + len() + "+" operatorfrom itertools import chain# initializing liststest_list1 = [1, 3, 4, 5, 2, 6]test_list2 = [3, 4, 8, 3, 10, 1]# printing the original listsprint ("The original list 1 is : " + str(test_list1))print ("The original list 2 is : " + str(test_list2))# Average of two lists# using sum() + len() + "+" operatorres = sum(chain(test_list1, test_list2)) / len(list(chain(test_list1, test_list2)))# printing resultprint ("The Average of both lists is : " + str(res)) |
The original list 1 is : [1, 3, 4, 5, 2, 6] The original list 2 is : [3, 4, 8, 3, 10, 1] The Average of both lists is : 4.166666666666667
Time Complexity: O(n)
Auxiliary Space: O(n)
Method #3 : Using extend() and mean() method of statistics module
extend() can be used to append a list into the other list and then statistics.mean() can be used to find the arithmetic mean of the new list that contains the elements from both the lists.
Python3
# Python3 code to demonstrate# Average of two listsimport statistics# initializing liststest_list1 = [1, 3, 4, 5, 2, 6]test_list2 = [3, 4, 8, 3, 10, 1]# printing the original listsprint("The original list 1 is : " + str(test_list1))print("The original list 2 is : " + str(test_list2))# Average of two listsx = []x.extend(test_list1)x.extend(test_list2)res = statistics.mean(x)# printing resultprint("The Average of both lists is : " + str(res)) |
The original list 1 is : [1, 3, 4, 5, 2, 6] The original list 2 is : [3, 4, 8, 3, 10, 1] The Average of both lists is : 4.166666666666667
Time Complexity: O(n*n), where n is the number of elements in the list “test_list”.
Auxiliary Space: O(n), where n is the number of elements in the list “test_list”.
Approach 4: Using zip() and map()
Using zip() to combine the elements of the two lists
Using map() to add the elements at the same index of both lists and divide by 2
Using sum() to find the sum of the resulting list
Using len() to find the length of the resulting list
Python3
#Using zip() and map()test_list1 = [1, 3, 4, 5, 2, 6]test_list2 = [3, 4, 8, 3, 10, 1]#Using zip() to combine the elements of the two lists#Using map() to add the elements at the same index of both lists and divide by 2#Using sum() to find the sum of the resulting list#Using len() to find the length of the resulting listres = sum(map(lambda x: (x[0] + x[1])/2, zip(test_list1, test_list2))) / len(test_list1)#printing resultprint("The Average of both lists is : " + str(res))#This code is contributed by Edula Vinay Kumar Reddy |
The Average of both lists is : 4.166666666666667
Time Complexity: O(n) where n is the length of the lists
Auxiliary Space : O(n)
Method #5: Using Functions, for loop
Python3
# function to calculate the average of two listsdef average_lists(list1, list2): # check if the lengths of the lists are equal if len(list1) != len(list2): return None # calculate the sum of the elements of both lists sum = 0 for i in range(len(list1)): sum += list1[i] + list2[i] # calculate the average and return it return sum / (2*len(list1))# example usagelist1 = [1, 3, 4, 5, 2, 6]list2 = [3, 4, 8, 3, 10, 1]average = average_lists(list1, list2)if average is not None: print("The Average of both lists is :", average)else: print("Lists are not of equal length") |
The Average of both lists is : 4.166666666666667
Time Complexity: O(n) where n is the length of the lists
Auxiliary Space : O(n)
