new_contents: # Copyright (c) 2014 ASMlover. All rights reserved. 
  #
  # Redistribution and use in source and binary forms, with or without 
  # modification, are permitted provided that the following conditions 
  # are met:
  #
  #  * Redistributions of source code must retain the above copyright 
  #    notice, this list ofconditions and the following disclaimer. 
  #
  #  * Redistributions in binary form must reproduce the above copyright 
  #    notice, this list of conditions and the following disclaimer in 
  #    the documentation and/or other materialsprovided with the 
  #    distribution.
  #
  # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 
  # "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 
  # LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 
  # FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 
  # COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 
  # INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 
  # BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 
  # LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 
  # CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 
  # LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN 
  # ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 
  # POSSIBILITY OF SUCH DAMAGE.
  #
  #!/usr/bin/env python
  # -*- encoding: utf-8 -*-
  
  import fileinput
  
  def add_line_number():
    for line in fileinput.input(inplace=True):
      line = line.rstrip()
      num = fileinput.lineno()
      print '%-40s # %2i' % (line, num)
  
  
  if __name__ == '__main__':
    add_line_number()
  
subject: add demo about using fileinput modules