title: Merge 2 columns to a new column in txt file using Python
body: <p>Helllo everyone, here is my txt file, I want to merge the first column and the second column to a new column, I tried to change the File extension to Excel, and use the <code>concatenate</code>command, but there are over 1000000 datas and the excel can only show the limited quantity, thus I will lost some datas. So I want to ask you professinal people wether there is a method in Python to merge 2 columns directly in txt file without format converting?   </p>
  
  <pre><code>Datum       Zeit        W [cm]      Status      DT-Index    W [mNHN]    
  01/05/2016  00:01:00    313,000000  U   42491,000694    -1,87   
  01/05/2016  00:02:00    313,000000  U   42491,001389    -1,87   
  01/05/2016  00:03:00    313,000000  U   42491,002083    -1,87   
  01/05/2016  00:04:00    313,000000  U   42491,002778    -1,87   
  ...... # over 1000000 datas
  </code></pre>
  
  <p>what I want:</p>
  
  <pre><code>Datum       Zeit        W [cm]      Status      DT-Index    W [mNHN]    Datetime
  01/05/2016  00:01:00    313,000000  U   42491,000694    -1,87       01/05/2016/00:01:00 
  01/05/2016  00:02:00    313,000000  U   42491,001389    -1,87       01/05/2016/00:02:00     
  01/05/2016  00:03:00    313,000000  U   42491,002083    -1,87       01/05/2016/00:03:00 
  01/05/2016  00:04:00    313,000000  U   42491,002778    -1,87       01/05/2016/00:04:00 
  ...... #over 1000000 datas
  </code></pre>