title: TypeError: Mismatch between array dtype ('object') and format specifier ('%.18e')
body: <p>I have the following array:</p>
  
  <pre><code>X = np.array([image_array_to_vector1,image_array_to_vector2,image_array_to_vector3,image_array_to_vector4])
  </code></pre>
  
  <p>A print out of <code>X</code> looks as follows:</p>
  
  <pre><code>[array([167, 167, 169, ...,   1,   1,   1], dtype=uint8)
   array([42, 43, 43, ..., 41, 36, 34], dtype=uint8)
   array([0, 0, 0, ..., 0, 0, 0], dtype=uint8)
   array([0, 0, 0, ..., 0, 0, 0], dtype=uint8)]
  </code></pre>
  
  <p>When I try to save the data as txt:</p>
  
  <pre><code>X_to_text_file = np.savetxt('x.txt',X)
  </code></pre>
  
  <p>I get the following:</p>
  
  <pre><code>File "/Library/Python/2.7/site-packages/numpy/lib/npyio.py", line 1258, in savetxt
      % (str(X.dtype), format))
  TypeError: Mismatch between array dtype ('object') and format specifier ('%.18e')
  </code></pre>
  
  <p>Why is that? How can I solve the issue?</p>
  
  <p>Thanks.</p>