title: how to reading .txt file , and adding space after specific position/index , for each line in python
body: <p>I want to read all line in txt.file, and add space at after specific position/index.</p>
  
  <p>suppose my file contains:</p>
  
  <pre><code> 1234567891011 12134516 17  
  </code></pre>
  
  <p>in the above file: I want to add space after index/position [8],[10],[16],and [20], means after irrerular position/index.</p>
  
  <p>expected output : </p>
  
  <pre><code> 123456789 10 11 121 3451 6 17
  </code></pre>
  
  <p>As a reminder: I don't want to replace elements, just add space after a specific position/index </p>
  
  <p>note: all line in the file as the same structure.</p>
  
  <p>reading and writing .txt file and add space after at specific positon/index.</p>
  
  <p>my file contain : </p>
  
  <pre><code> 1234567891011 12134516 17 
  
   6546546546456 35654554 54
  </code></pre>
  
  <p>expected output :</p>
  
  <pre><code> 123456789 10 11 121 3451 6 17 
  
   654654654 64 56 356 5455 4 54
  </code></pre>