title: Remove every second row of array multiple times
body: <p>So I have several .txt files with over +80.000 rows of data.
  As such this might not be much for Python, however, I need to use this data in R where I need a certain package. And over there it takes around 30 sec to load one file - and I have 1200 of these files.</p>
  
  <p>However, the data in these files are rather dense. There is no need to have such small steps, i.e. I want to remove some in order to make the file smaller.</p>
  
  <p>What I'm using now is as follows:</p>
  
  <pre><code>np.delete(np.array(data_lines), np.arange(1, np.array(data_lines).size, 2))
  </code></pre>
  
  <p>I make it start at the row index 1, and the remove every second row of the <code>data_lines</code> array containing the +80.000 lines of data. However, as you can see, this only reduces the rows with 1/2. And I probably need at least a 1/10 reduction. So in principle I could probably just do some kind of loop to do this, but I was wondering if there was a smarter way to achieve it ?</p>