old_contents: #!/usr/bin/env python
  
  import os
  import os.path
  import sys
  import pdb
  import shutil
  
  def relative_ln_s( from_, to_ ):
      """
  
      This is just so dirty & boring: create a relative symlink, making the
      to_ path relative to from_. No errorchecks. Both arguments must be
      files, a destination directory doesn't work (I think). An existing
      file in to_ will be removed.
  
      """
      prefix = os.path.commonprefix( [ to_, from_ ] )
      if prefix == '':
          prefix = '/'
      source = from_.split( prefix )[ 1 ]
      dest   = to_.split( prefix )[ 1 ]
      level = len( dest.split( '/' ) ) - 1
      path =  ( '../' * level ) + source
      return path
  
  USAGE = 'Usage: make_rel_symlink [-p]  <sourcefile> <destfile>'
  
  just_print = False;
  if sys.argv[1] == "-p":
      just_print = True;
      sys.argv = sys.argv[ 1:]
  
  if len( sys.argv ) != 3:
      print USAGE
      sys.exit( 1 )
  
  if  os.path.isdir(  sys.argv[2] ):
      print "Removing link target dir:" +  sys.argv[2]
      shutil.rmtree( sys.argv[2])
  
  link_path = relative_ln_s( sys.argv[1], sys.argv[2] )
  if just_print:
      print link_path
  else:
      os.chdir( os.path.dirname( sys.argv[2]))
      target = os.path.basename( sys.argv[2])
      if os.path.exists( target ):
          os.unlink( target)
      os.symlink( link_path, target)
  
  
  
new_contents: #!/usr/bin/env python3
  
  import os
  import os.path
  import sys
  import pdb
  import shutil
  
  def relative_ln_s( from_, to_ ):
      """
  
      This is just so dirty & boring: create a relative symlink, making the
      to_ path relative to from_. No errorchecks. Both arguments must be
      files, a destination directory doesn't work (I think). An existing
      file in to_ will be removed.
  
      """
      prefix = os.path.commonprefix( [ to_, from_ ] )
      if prefix == '':
          prefix = '/'
      source = from_.split( prefix )[ 1 ]
      dest   = to_.split( prefix )[ 1 ]
      level = len( dest.split( '/' ) ) - 1
      path =  ( '../' * level ) + source
      return path
  
  USAGE = 'Usage: make_rel_symlink [-p]  <sourcefile> <destfile>'
  
  just_print = False;
  if sys.argv[1] == "-p":
      just_print = True;
      sys.argv = sys.argv[ 1:]
  
  if len( sys.argv ) != 3:
      print(USAGE)
      sys.exit( 1 )
  
  if  os.path.isdir(  sys.argv[2] ):
      print("Removing link target dir:" +  sys.argv[2])
      shutil.rmtree( sys.argv[2])
  
  link_path = relative_ln_s( sys.argv[1], sys.argv[2] )
  if just_print:
      print(link_path)
  else:
      os.chdir( os.path.dirname( sys.argv[2]))
      target = os.path.basename( sys.argv[2])
      if os.path.exists( target ):
          os.unlink( target)
      os.symlink( link_path, target)
  
  
  
subject: Make make_rel_symlink.py use python3.