title: numpy.loadtxt "could not convert string to float"
body: <p>A minimal example that reproduces this is:</p>
  
  <pre><code>import numpy
  numpy.loadtxt("data.txt", delimiter='\t')
  </code></pre>
  
  <p>with <code>data.txt</code> being:</p>
  
  <pre><code>    A   R   N   D   C   Q
  A   5   -2  -1  -2  -1  -1
  R   -2  7   -1  -2  -4  1
  N   -1  -1  7   2   -2  0
  </code></pre>
  
  <p>When running the code I get a ValueError:</p>
  
  <pre><code>[root@mycomp]$ python Needleman-Wunsch.py 
  Traceback (most recent call last):
      File "Needleman-Wunsch.py", line 92, in &lt;module&gt;
          (alignedSeq1, alignedSeq2) = computeFMatrix(seq1, seq2, -6)
      File "Needleman-Wunsch.py", line 34, in computeFMatrix
          similarityMatrixMap = readBLOSUM50("BLOSUM50.txt")
      File "Needleman-Wunsch.py", line 16, in readBLOSUM50
          similarityMatrix = np.loadtxt(fileName, delimiter='\t')
      File "/usr/local/lib/python2.7/site-packages/numpy/lib/npyio.py", line 827, in loadtxt
          items = [conv(val) for (conv, val) in zip(converters, vals)]    
      ValueError: could not convert string to float: A  R  N  D  C  Q  E  G  H  I  L  K  M  F  P  S  T  W  Y  V
  </code></pre>
  
  <p>You can also have <a href="https://code.google.com/p/compscimed/source/browse/alignment/blosum50.txt" rel="nofollow noreferrer">the original <code>BLOSUM50.txt</code> file</a> and the full code is from <a href="http://www.codesofmylife.com/2011/04/10/needleman-wunsch-algorithm-for-global-sequence-alignment-in-python/" rel="nofollow noreferrer">the link above</a>.</p>
  
  <p>Erasing the first line of <code>BLOSUM50.txt</code> gave the same error.</p>