title: Syntax error when casting string to int
body: <p>My code:</p>
  
  <pre><code>def digit_sum(n):
      result = 0
      s = str(n)
      for c in s:
          result += (int)c    # invalid syntax??????????
      return result
  
  print digit_sum(1234)
  </code></pre>
  
  <p>Result:</p>
  
  <pre><code>    result += (int)c    # invalid syntax??????????
                     ^
  SyntaxError: invalid syntax
  </code></pre>
  
  <p>The function is supposed to return the sum of each digit of the argument "n".
  Why do I get <code>SyntaxError</code> in the commented line? The variable <code>c</code> is of type <code>str</code>ing so it shouldn´t be an issue to apply a type cast to <code>int</code>.</p>