The Harmonic Mean function in Python (scipy.stats.hmean) requires that the input be positive numbers.
For example:
from scipy import st
There is a statistics library if you are using Python >= 3.6:
https://docs.python.org/3/library/statistics.html
You may use its mean method like this. Let's say you have a list of numbers of which you want to find mean:
list = [11, 13, 12, 15, 17]
import statistics as s
s.harmonic_mean(list)
It has other methods too like stdev, variance, mode, mean, median etc which too are useful.