title: Python Pandas read_csv with nrows=1
body: <p>I have this code reading a text file with headers. ANd append another file with the same headers to it. As the main file is very huge, I only want to read in part of it and get the column headers.
  I will get this error if the only line there is the header. And I do not have an idea of how many rows the file has. What I would like to achieve is to read in the file and get the column header of the file. Because I want to append another file to it, I am trying to ensure that the columns are correct.</p>
  
  <pre><code>    import pandas as pd
      main = pd.read_csv(main_input, nrows=1)
      data = pd.read_csv(file_input)
      data = data.reindex_axis(main.columns, axis=1)
      data.to_csv(main_input,
                  quoting=csv.QUOTE_ALL,
                  mode='a', header=False, index=False)
  </code></pre>
  
  <p>Examine the stack trace:</p>
  
  <pre><code>    Traceback (most recent call last):
      File "&lt;stdin&gt;", line 1, in &lt;module&gt;
      File "C:\Users\gohm\AppData\Local\Continuum\Anaconda\lib\site-packages\pandas\io\parsers.py", line 420, in parser_f
      return _read(filepath_or_buffer, kwds)
      File "C:\Users\gohm\AppData\Local\Continuum\Anaconda\lib\site-packages\pandas\io\parsers.py", line 221, in _read
      return parser.read(nrows)
      File "C:\Users\gohm\AppData\Local\Continuum\Anaconda\lib\site-packages\pandas\io\parsers.py", line 626, in read
      ret = self._engine.read(nrows)
      File "C:\Users\gohm\AppData\Local\Continuum\Anaconda\lib\site-packages\pandas\io\parsers.py", line 1070, in read
      data = self._reader.read(nrows)
      File "parser.pyx", line 727, in pandas.parser.TextReader.read (pandas\parser.c:7110)
      File "parser.pyx", line 774, in pandas.parser.TextReader._read_low_memory (pandas\parser.c:7671)
      StopIteration
  </code></pre>