How to calculate a logistic sigmoid function in Python?

Question

This is a logistic sigmoid function:

I know x. How can I calculate F(x

Answer 1

Good answer from @unwind. It however can't handle extreme negative number (throwing OverflowError).

My improvement:

def sigmoid(x):
    try:
        res = 1 / (1 + math.exp(-x))
    except OverflowError:
        res = 0.0
    return res