title: Reading in ascii data lines with missing cells?
body: <p>I have an ascii file that has 3 lines of data that looks like this:</p>
  
  <pre><code>Timestamp: 00:47:14 SATID 13 VAL1 28 VAL2 227 SIGNAL 37                                     SATID 15 VAL1 22 VAL2 265 SIGNAL 30 SATID 16 VAL1 22 VAL2 265 SIGNAL 30
  Timestamp: 00:48:14 SATID 13 VAL1 28 VAL2 227 SIGNAL 37                                     SATID 15 VAL1 22 VAL2 265 SIGNAL nan SATID 16 VAL1 22 VAL2 265 SIGNAL 30
  Timestamp: 00:49:14                                     SATID 14 VAL1 22 VAL2 265 SIGNAL 30
  </code></pre>
  
  <p>(Please see image for original formatting). <a href="https://i.stack.imgur.com/gdoEn.png" rel="nofollow noreferrer">original ascii data format </a>When I try to read it into Python, though, I get the following error:</p>
  
  <pre><code>time,sat1,sat2,sat3,sat4 = np.loadtxt("test1.asc", usecols=(1,9,17,25,33), unpack=True, converters = {1: strpdate2num("%H:%M:%S")})
  Traceback (most recent call last):
  File "&lt;stdin&gt;", line 1, in &lt;module&gt;
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/numpy/lib/npyio.py", line 839, in loadtxt
  vals = [vals[i] for i in usecols]
  IndexError: list index out of range
  </code></pre>
  
  <p>Does anyone know how I can do so that Python ignores the empty cells and read whatever data is available in each column?</p>
  
  <p>Thanks!</p>