title: Count the number of times a particular string appears in a given word
body: <p>How to write a program that prints the number of times a particular string appears in a given word.
  For example: if I'm looking for the string 'dad' in a word 'asdadgfrdad'
               output should be 2.</p>
  
  <pre class="lang-py prettyprint-override"><code>def numStrings(a):
      strings = 'dad'
      result = 0
      for char in a:
          if char in strings:
              result = result + 1
      print result
  
  numStrings("asdadgfrdad")
  </code></pre>
  
  <p>But this gives me the number of times the letters d,a are present in the given word. How to correct this?</p>