title: genfromtxt returning -1 and nan rows
body: <p>I am trying to read a txt file with numpy and I have the following code</p>
  
  <pre><code>import numpy as np
  def parsefile(filename):
      return np.genfromtxt(filename,
                       delimiter = dly_delimiter,
                       usecols = dly_usecols,
                       dtype = dly_dtype,
                       skip_header = 4,
                       names = dly_names)
  dly_delimiter = [7,5,9,13,10,13,9,13,10,13,10]
  dly_usecols = [1,7]
  dly_dtype = [np.int32, np.float64]
  dly_names = ['node number', 'z_force']
  force = parsefile('nodfor')
  print(force)
  </code></pre>
  
  <p>And the following comes out</p>
  
  <pre><code>[(-1, nan) (-1, nan) (-1, nan) ..., (-1, nan) (-1, nan) (-1, nan)]
  </code></pre>
  
  <p>But what I am interested in are the number after 'nd#' and the number after 'zforce'.</p>
  
  <p>[<a href="https://i.stack.imgur.com/Np2Dn.png" rel="nofollow noreferrer">the format of the txt file is like this]
  </a>and this is a snippet of the txt file (two lines):</p>
  
  <pre><code> nd#   39584  xforce=   0.0000E+00   yforce=   0.0000E+00  zforce=   
  0.0000E+00   energy=   0.0000E+00   setid =       1
   nd#   39585  xforce=   0.0000E+00   yforce=   0.0000E+00  zforce=   
  0.0000E+00   energy=   0.0000E+00   setid =       1
  </code></pre>
  
  <p>Is this a known issue. How can I fix this?</p>