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Example: x = [[1,3,2],[4,5,6],[7,8,9]]

I attempted to use:

sum(x) / len(x) but it seems to give me this error

(TypeError: unsupported operand type(s) for +: 'int' and 'list')

The list is inputted by the user with command: average_list() and could contain any amount of numbers per square brackets.

You can sum the sums of the inner lists:

x = [[1,3,2],[4,5,6],[7,8,9]]



s = sum(sum(a) for a in x)

l = sum(len(a) for a in x)

print(s / l) # 5.0

Use numpy

import numpy as np



x = np.array(x)

avg = np.sum(x)/np.size(x) # avg = 5

x = [i for sublist in x for i in sublist]

avg = sum(x)/len(x)

Here is an answer after flattening the list

This provides you both, the average of the lists of list as well as the average of complete list.

x = [[1,3,2],[4,5,6],[7,8,9]]

new_list = [sum(l)/len(l) for l in x]

print(sum(new_list)/len(new_list))

Output:

5.0

A more scholastic way to do this is the following:

x = [[1,3,2],[4,5,6],[7,8,9]]



#stripping square brackets

elementsString = ''.join( c for c in str(x) if  c not in '' )



total = 0

numberOfElements = 0



#converting the string numbers into int

for i in elementsString.split(','):

    #using int but can be also float for example

    i = int(i) 

    numberOfElements += 1

    total += i



average = total/numberOfElements

print(average)



#5.0 is the answer in your case

are you trying to find the average of the sum of the entire list of (x) or the sum of each cell?