title: Count lower case characters in a string
body: <p>What is the most pythonic and/or efficient way to count the number of characters in a string that are lowercase?</p>
  
  <p>Here's the first thing that came to mind:</p>
  
  <pre><code>def n_lower_chars(string):
      return sum([int(c.islower()) for c in string])
  </code></pre>