title: Scipy Differential Evolution with integers
body: <p>I'm trying to run an optimization with scipy.optimize.differential_evolution. The code calls for bounds for each variable in x. But I want to a solution where parts of x must be integers, while others can range freely as floats.  The relevant part of my code looks like </p>
  
  <pre><code>    bounds = [(0,3),(0,3),(0,3),???,???]
      result = differential_evolution(func, bounds)
  </code></pre>
  
  <p>What do I replace the ???'s with to force those variables to be ints in a given range?</p>