title: String equivalent of +=
body: <p>Is there an equivalent of += for a string?</p>
  
  <p>ie:   </p>
  
  <pre><code>x = 1
  while x &lt;= 100:
      y = x
      if x % 3 == 0:
          y = 'Fizz'
      if x % 5 == 0:
          y += 'Buzz'
      if x % 7 == 0:
          y += 'Foo'
      if x % 11 == 0:
          y += 'Bar'
      print y
      x += 1
  raw_input('Press enter to exit...')
  </code></pre>
  
  <p>This should return <code>a string and a second string</code> if the same rules as with numbers applied. Is it possible to do this? Because just doing that returns <code>TypeError: unsupported operand type(s) for +=: 'int' and 'str'</code>, even though <code>y</code> is a string to begin with, not an <code>int</code>.</p>