Find average of a list in python

Prerequisites: sum() function, len() function, round() function, reduce(), lambda, and mean(). Given a list of numbers, the task is to find average of that list. Average is the sum of elements divided by the number of elements.

Input : [4, 5, 1, 2, 9, 7, 10, 8]
Output : Average of the list = 5.75
Explanation:
Sum of the elements is 4+5+1+2+9+7+10+8 = 46
and total number of elements is 8.
So average is 46 / 8 = 5.75

Input : [15, 9, 55, 41, 35, 20, 62, 49]
Output : Average of the list = 35.75
Explanation:
Sum of the elements is 15+9+55+41+35+20+62+49 = 286
and total number of elements is 8.
So average is 46 / 8 = 35.75

Using sum()

In Python we can find the average of a list by simply using the sum() and len() function.

• sum() : Using sum() function we can get the sum of the list.
• len() : len() function is used to get the length or the number of elements in a list.

Python3

# Python program to get average of a list
def Average(lst):
    return sum(lst) / len(lst)

# Driver Code
lst = [15, 9, 55, 41, 35, 20, 62, 49]
average = Average(lst)

# Printing average of the list
print("Average of the list =", round(average, 2))

Output

Average of the list = 35.75

Time Complexity: O(n) where n is the length of the list.
Auxiliary Space: O(1) as we only require a single variable to store the average.

Using reduce() and lambda

We can use the reduce() to reduce the loop and by using the lambda function can compute summation of list. We use len() to calculate length as discussed above. 

Python3

# Python program to get average of a list
# Using reduce() and lambda

# importing reduce()
from functools import reduce

def Average(lst):
    return reduce(lambda a, b: a + b, lst) / len(lst)

# Driver Code
lst = [15, 9, 55, 41, 35, 20, 62, 49]
average = Average(lst)

# Printing average of the list
print("Average of the list =", round(average, 2))

Output

Average of the list = 35.75

Time complexity: O(n), where n is the length of the list lst.
Auxiliary space: O(1). The space used is constant and independent of the size of the input list.

Using mean()

The inbuilt function mean() can be used to calculate the mean( average ) of the list. 

Python3

# Python program to get average of a list
# Using mean()

# importing mean()
from statistics import mean

def Average(lst):
    return mean(lst)

# Driver Code
lst = [15, 9, 55, 41, 35, 20, 62, 49]
average = Average(lst)

# Printing average of the list
print("Average of the list =", round(average, 2))

Output

Average of the list = 35.75

Time complexity: O(n), where n is the length of the list.
Auxiliary space: O(1).

By iterating list

Iterating list using for loop and doing operations on each element of list.

Python3

# Python code to get average of list
def Average(lst):
    sum_of_list = 0
    for i in range(len(lst)):
        sum_of_list += lst[i]
    average = sum_of_list/len(lst)
    return average


# Driver Code
lst = [15, 9, 55, 41, 35, 20, 62, 49]
average = Average(lst)
print("Average of the list =", round(average, 2))

Output

Average of the list = 35.75

Time complexity: O(n) 
Auxiliary space: O(n), where n is the length of list.

Using numpy.average() function

Python3

#importing numpy module
import numpy
#function for finding average
def Average(lst):
  #average function
  avg = numpy.average(lst)
  return(avg)
#input list
lst = [15, 9, 55, 41, 35, 20, 62, 49]
#function call
print("Average of the list =",round(Average(lst),2))

Output

Average of the list = 35.75