title: How to read a csv file one line at a time and replace/edit certain lines as you go?
body: <p>I have a 60GB csv file I need to make some modifications to. The customer wants some changes to the files data, but I don't want to regenerate the data in that file because it took 4 days to do.</p>
  
  <p>How can I read the file, line by line (not loading it all into memory!), and make edits to those lines as I go, replacing certain values etc.?</p>