title: Does a heaviside step function exist?
body: <p>Is there a <a href="http://en.wikipedia.org/wiki/Heaviside_step_function">heaviside</a> function in Python similar to that of MATLAB's <a href="http://www.mathworks.co.uk/help/symbolic/heaviside.html"><code>heaviside</code></a>?</p>
  
  <p>I am struggling to find one.</p>