Python – Ways to find Geometric Mean in List

While working with Python, we can have a problem in which we need to find geometric mean of a list cumulative. This problem is common in Data Science domain. Let’s discuss certain ways in which this problem can be solved. 
Method #1 : Using loop + formula The simpler manner to approach this problem is to employ the formula for finding geometric mean and perform using loop shorthands. This is the most basic approach to solve this problem. 

Python3

# Python3 code to demonstrate working of
# Geometric Mean of List
# using loop + formula
import math

# initialize list
test_list = [6, 7, 3, 9, 10, 15]

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

# Geometric Mean of List
# using loop + formula
temp = 1
for i in range(0, len(test_list)) :
    temp = temp * test_list[i]
temp2 = (float)(math.pow(temp, (1 / len(test_list))))
res = (float)(temp2)

# printing result
print("The geometric mean of list is : " + str(res))

Output : 

The original list is : [6, 7, 3, 9, 10, 15]
The geometric mean of list is : 7.443617568993922

Time Complexity: O(n), where n is the length of the input list. This is because we’re using the loop + formula which has a time complexity of O(n) in the worst case.
Auxiliary Space: O(1), as we’re using constant additional space

Method #2 : Using statistics.geometric_mean() This task can also be performed using inbuilt function of geometric_mean(). This is new in Python versions >= 3.8. 

Python3

# Python3 code to demonstrate working of
# Geometric Mean of List
# using statistics.geometric_mean()
import statistics

# initialize list
test_list = [6, 7, 3, 9, 10, 15]

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

# Geometric Mean of List
# using statistics.geometric_mean()
res = statistics.geometric_mean(test_list, 1)

# printing result
print("The geometric mean of list is : " + str(res))

Output : 

The original list is : [6, 7, 3, 9, 10, 15]
The geometric mean of list is : 7.443617568993922

Time Complexity: O(n), where n is the number of elements in the list “test_list”.
Auxiliary Space: O(1), constant extra space is required

Method #3: Using numpy library

Note: Install numpy module using command “pip install numpy”

We can use the numpy library which has a numpy.prod() function to find the product of all elements in the list and then use numpy.power() function with the reciprocal of the length of the list as the exponent to find the geometric mean.

Python

import numpy as np

# initialize list
test_list = [6, 7, 3, 9, 10, 15]

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

# Geometric Mean of List using numpy
result = np.power(np.prod(test_list), 1/len(test_list))

# printing result
print("The geometric mean of list is : " + str(result))
#This code is contributed by Edula Vinay Kumar Reddy

Output:

The original list is : [6, 7, 3, 9, 10, 15]
The geometric mean of list is : 7.443617568993922

Time complexity: O(n)
Auxiliary space: O(1)