title: How can i read CSV file in pandas with Nan?
body: <p>I have a txt file:</p>
  
  <pre><code>24688 1965 12 31 12   0  0    0.0 -48.3
  24688 1965 12 31 15   0  0        -47.2
  24688 1965 12 31 18   0  0        -49.0
  24688 1965 12 31 21   0  0    0.0 -48.1
  24688 1966  1  1  0   0  0    0.0 -52.5
  </code></pre>
  
  <p>..........</p>
  
  <p>I'm trying to get this DataFrame used 
  <code>data = pd.read_csv('/home/igor/py/normdata.txt', header=None, sep='\s+')</code></p>
  
  <pre><code>24688 1965 12 31 12   0  0    0.0 -48.3
  24688 1965 12 31 15   0  0    Nan -47.2
  24688 1965 12 31 18   0  0    Nan -49.0
  24688 1965 12 31 21   0  0    0.0 -48.1
  24688 1966  1  1  0   0  0    0.0 -52.5
  </code></pre>
  
  <p>But i get:</p>
  
  <pre><code>24688   1965    12  31  12  0.0 0.0 0.0 -48.3
  24688   1965    12  31  15  0.0 0.0 -47.2 Nan
  24688   1965    12  31  18  0.0 0.0 -49.0 Nan
  24688   1965    12  31  21  0.0 0.0 0.0 -48.1
  24688   1966    1   1   0   0.0 0.0 0.0 -52.5
  </code></pre>
  
  <p>Can anyone help me?</p>