title: only first line of output gets printed to my text file
body: <p>I have a text file which I read in and then I extract the data I require and try sending it to different new text file, but only the first line gets into the new text file.</p>
  
  <pre><code>    import csv
      f = open('C:\\Users\\c\\Documents\\DCX.txt')
      next(f)
      csv_f=csv.reader(f, delimiter='\t')
      for row in csv_f:
          if 'DCX3520E' in row[0] and 'NULL' not in row[6]:
              with open("out.txt","w") as f1:
                  dcx = row[0] + " " + row[6]
                  aa = dcx[9:]
                  print(aa)
                  f1.writelines(aa)
  </code></pre>