python: getting around division by zero

Question

I have a big data set of floating point numbers. I iterate through them and evaluate np.log(x) for each of them. I get

RuntimeWarning: divide b         


        

Answer 1

Since the log for x=0 is minus infinite, I'd simply check if the input value is zero and return whatever you want there:

def safe_ln(x):
    if x <= 0:
        return 0
    return math.log(x)

EDIT: small edit: you should check for all values smaller than or equal to 0.

EDIT 2: np.log is of course a function to calculate on a numpy array, for single values you should use math.log. This is how the above function looks with numpy:

def safe_ln(x, minval=0.0000000001):
    return np.log(x.clip(min=minval))