title: TypeError: Mismatch between array dtype ('float64') and format specifier
body: <p>I have a numpy array with dimension 1000*30*150. I am trying to save it as txt file. So far I have tried this</p>
  
  <pre><code>np.savetxt("test.txt", mydata, fmt='%.5f', delimiter=",")
  #and 
  with open('test.txt', 'w') as f:
      for row in mydata:
          np.savetxt(f, row, delimiter=',', fmt='%.5f')
  </code></pre>
  
  <p>both method give me error </p>
  
  <pre><code>Traceback (most recent call last):
    File "/usr/local/lib/python3.5/dist-packages/numpy/lib/npyio.py", line 1254, in savetxt
      fh.write(asbytes(format % tuple(row) + newline))
  TypeError: only length-1 arrays can be converted to Python scalars
  
  During handling of the above exception, another exception occurred:
  
  Traceback (most recent call last):
  
  
          np.savetxt("test.txt", train, fmt='%.5f', delimiter=",")
        File "/usr/local/lib/python3.5/dist-packages/numpy/lib/npyio.py", line 1258, in savetxt
          % (str(X.dtype), format))
      TypeError: Mismatch between array dtype ('float64') and format specifier ('%.5f,%.5f,%.5f,%.5f,%.5f,%.5f,%.5f,%.5f,%.5f,%.5f,%.5f,%.5f,%.5f,%.5f,%.5f,%.5f,%.5f,%.5f,%.5f,%.5f,%.5f,%.5f,%.5f,%.5f')
  </code></pre>