How to calculate a logistic sigmoid function in Python?
<p>This is a logistic sigmoid function:</p>

<p><img src="http://i.stack.imgur.com/KxJZI.gif" alt="alt text"></p>

<p>I know x. How can I calculate F(x) in Python now?</p>

<p>Let's say x = 0.458.</p>

<p>F(x) = ?</p>
