title: python read_fwf error: 'dtype is not supported with python-fwf parser'
body: <p>Using python 2.7.5 and pandas 0.12.0, I'm trying to import fixed-width-font text files into a DataFrame with 'pd.io.parsers.read_fwf()'.  The values I'm importing are all numeric, but it's important that leading zeros be preserved, so I'd like to specify the dtype as string rather than int.</p>
  
  <p>According to the <a href="http://pandas.pydata.org/pandas-docs/stable/generated/pandas.io.parsers.read_fwf.html#pandas.io.parsers.read_fwf">documentation for this function</a>, the dtype attribute is supported in read_fwf, but when I try to use it:</p>
  
  <p><code>data= pd.io.parsers.read_fwf(file, colspecs = ([79,81], [87,90]), header = None, dtype = {0: np.str, 1: np.str})</code></p>
  
  <p>I get the error:</p>
  
  <p><code>ValueError: dtype is not supported with python-fwf parser</code></p>
  
  <p>I've tried as many variations as I can think of for setting 'dtype = something', but all of them return the same message.  </p>
  
  <p>Any help would be much appreciated!    </p>