title: Python find first occurrence of character after index
body: <p>I am trying to get the index of the first occurrence of a character that occurs in a string <em>after</em> a specified index. For example:</p>
  
  <pre><code>string = 'This + is + a + string'
  
  # The 'i' in 'is' is at the 7th index, find the next occurrence of '+'
  string.find_after_index(7, '+')
  
  # Return 10, the index of the next '+' character
  &gt;&gt;&gt; 10
  </code></pre>