Expanding Mean

Problem

Compute the expanding (cumulative) mean of a series. The output at position i is the mean of the first i + 1 observations: sum(x[0:i+1]) / (i + 1).

An empty series yields an empty list.

Hint

Keep a running total instead of recomputing the sum each step.

case 1

in: [[1,2,3,4]]

expected: [1,1.5,2,2.5]

case 2

in: [[5]]

expected: [5]

case 3

in: [[2,4,6]]

expected: [2,3,4]

case 4

in: [[]]

expected: []

Starter codePython

def expanding_mean(series):
    # Your code here
    pass

4 test cases · run your code against them in the editor