Harmonic mean in a python function?

Question

I have 2 functions that give out precision and recall scores, I need to make a harmonic mean function defined in the same library that uses these two scores. The functions looks

Answer 1

With a slight change of your F1 function, and with the same precision and recall function you defined, I have this working:

def F1(precision, recall):
    return (2*precision*recall)/(precision+recall)

r = [0,1,0,0,0,1,1,0,1]
h = [0,1,1,1,0,0,1,0,1]
p = precision(r, h)
rec = recall(r, h)
f = F1(p, rec)
print f

Review especially the use of variables I have. You must compute the result of each function and pass them to the F1 function.

Answer 2

The following will work with any number of arguments:

def hmean(*args):
    return len(args) / sum(1. / val for val in args)

To compute the harmonic mean of precision and recall, use:

result = hmean(precision, recall)

There are two problems with your function:

1. It fails to return a value.
2. On some versions of Python, it would use integer division for integer arguments, truncating the result.