title: Issue with CSV file when file is large
body: <p>I have a large tsv file (~2.5Gb). I iterate over each line where the line has 6 tabs. I take the first tab of each line and append the line to a csv file that is based on this first tab. The goal is to end with a file sorted with csv files based off of the master tsv lines.</p>
  
  <p>This works on a small scale file, but when I run on a large file the IPython console never concludes. The file I am saving to looks as if it is being filled, but when I open it nothing is shown.</p>
  
  <pre><code>import csv
  
  file_path = ".../master.tsv"
  
  with open(file_path, 'r') as masterfile:
      for line in masterfile:
          line_split = line.split("|")
          cik = line_split[0].zfill(10)
  
          save_path = ".../data-sorted/"
          save_path += cik + ".csv"
  
          with open(save_path, 'a') as savefile:
              wr = csv.writer(savefile, quoting=csv.QUOTE_ALL)
              wr.writerow(line_split)
  </code></pre>