title: Extract specific text lines?
body: <p>I have a large several hudred thousand lines text file. I have to extract 30,000 specific lines that are all in the text file in random spots. This is the program I have to extract one line at a time:</p>
  
  <pre><code>big_file = open('C:\\gbigfile.txt', 'r')
  small_file3 = open('C:\\small_file3.txt', 'w')
  for line in big_file:
     if 'S0414' in line:
        small_file3.write(line)
  gbigfile.close()
  small_file3.close()
  </code></pre>
  
  <p>How can I speed this up for 30,000 lines that I need to look up>?</p>