title: Python enumerate downwards or with a custom step
body: <p>How to make Python's <a href="https://docs.python.org/2/library/functions.html#enumerate" rel="noreferrer"><code>enumerate</code></a> function to enumerate from bigger numbers to lesser (descending order, decrement, count down)? Or in general, how to use different step increment/decrement in <code>enumerate</code>?</p>
  
  <p>For example, such function, applied to list <code>['a', 'b', 'c']</code>, with start value <code>10</code> and step <code>-2</code>, would produce iterator <code>[(10, 'a'), (8, 'b'), (6, 'c')]</code>.</p>