title: find position of a substring in a string
body: <p>i am having a python string of format</p>
  
  <pre><code>mystr = "hi.this(is?my*string+"
  </code></pre>
  
  <p>here i need to get the position of 'is' that is surrounded by special characters or non-alphabetic characters (i.e. second 'is' in this example). however, using </p>
  
  <pre><code>mystr.find('is')
  </code></pre>
  
  <p>will return the position if 'is' that is associated with 'this' which is not desired. how can i find the position of a substring that is surrounded by non-alphabetic characters in a string? using python 2.7</p>