title: Append columns to empty numpy array in python
body: <p>I have to fill a text file with columns of data, showing variation of some variables in time. For each variable I want to create a column array and then concatenate them all in a single matrix to be written to the text file. I do:</p>
  
  <pre><code>import numpy as np
  result = np.empty((0,1))    
  for data in [var1 var2 var3 var4]
    results_tmp = np.empty((0,1))
    for i in len(data):
        results_tmp = np.append(results_tmp, [data[i]], axis=0)
  </code></pre>
  
  <p>how do I fill the <code>result</code> array with the <code>results_tmp</code> columns?</p>