title: TypeError: 'int' object is not iterable // numpy
body: <p>Here is my function:</p>
  
  <pre><code>import numpy as np
  def calc_mean():
      return np.loadtxt('GOOG.csv', skiprows=1, usecols=(6)).mean(axis=0)
  </code></pre>
  
  <p>Here is my <code>GOOG.csv</code>:</p>
  
  <pre><code>Date        Open    High    Low     Close   Volume     Adj Close # &lt;-- column that I need
  2013-09-27  874.82  877.52  871.31  876.39  1258800    876.39
  2013-09-26  878.3   882.75  875     878.17  1259900    878.17
  2013-09-25  886.55  886.55  875.6   877.23  1649000    877.23
  2013-09-24  886.5   890.1   881.4   886.84  1467000    886.84
  2013-09-23  896.15  901.59  885.2   886.5   1777400    886.5
  2013-09-20  898.39  904.13  895.62  903.11  4345300    903.11
  2013-09-19  905.99  905.99  895.4   898.39  1597900    898.39
  2013-09-18  886.35  903.97  883.07  903.32  1934700    903.32
  2013-09-17  887.41  888.39  881     886.11  1259400    886.11
  2013-09-16  896.2   897     884.87  887.76  1336500    887.76
  .............................................................
  end of file:
  .............................................................
  2012-06-29  574.96  58013   572.20  580.07  2519500    580.07
  2012-06-28  565.90  566.23  557.21  564.31  1920900    564.31
  2012-06-27  567.70  573.99  566.02  569.30  1692300    569.30
  2012-06-26  562.76  566.60  559.48  564.68  1350200    564.68
  2012-06-25  567.33  568.09  557.35  560.70  1581600    560.70
  </code></pre>
  
  <p>When I run it, i have the following error:</p>
  
  <pre><code>  Traceback (most recent call last):
  File "/home/misha/Documents/finance/finance.py", line 164, in &lt;module&gt;
    security_mean(file_list)
  File "/home/misha/Documents/finance/finance.py", line 125, in security_mean
    return np.loadtxt('GOOG.csv', skiprows=1, usecols=(6)).mean(axis=0)
  File "/usr/lib/python2.7/site-packages/numpy/lib/npyio.py", line 703, in loadtxt
    usecols = list(usecols)
  TypeError: 'int' object is not iterable 
  </code></pre>
  
  <p>How can I fix that?</p>
  
  <p>if I change <code>usecols=(6)</code> on <code>usecols=(6,)</code> or <code>usecols=([6])</code> i have the following error:</p>
  
  <pre><code>Traceback (most recent call last):
    File "/home/misha/Documents/finance/finance.py", line 164, in &lt;module&gt;
      security_mean(file_list)
    File "/home/misha/Documents/finance/finance.py", line 125, in security_mean
      return np.loadtxt('GOOG.csv', skiprows=1, usecols=([6])).mean(axis=0)
    File "/usr/lib/python2.7/site-packages/numpy/lib/npyio.py", line 825, in loadtxt
      vals = [vals[i] for i in usecols]
  IndexError: list index out of range
  </code></pre>
  
  <p>Thanks.</p>
  
  <p><strong>NOTE:</strong> all data in <code>GOOG.csv</code> are <code>strings</code></p>