new_contents: #!/usr/bin/env python3
  'Convert Python source code to HTML with colorized markup'
  
  __all__ = ['colorize', 'build_page', 'default_css', 'default_html']
  
  import keyword, tokenize, cgi, functools
  
  def insert(s, i, text):
      'Insert text at position i in string s'
      return s[:i] + text + s[i:]
  
  def is_builtin(s):
      'Return True if s is the name of a builtin'
      return s in vars(__builtins__)
  
  def colorize(source):
      'Convert Python source code to an HTML fragment with colorized markup'
      text = cgi.escape(source)
      lines = text.splitlines(True)
      readline = functools.partial(next, iter(lines), '')
      actions = []
      kind = tok_str = ''
      tok_type = tokenize.COMMENT
      for tok in tokenize.generate_tokens(readline):
          prev_tok_type, prev_tok_str = tok_type, tok_str
          tok_type, tok_str, (srow, scol), (erow, ecol), logical_lineno = tok
          kind, prev_kind = '', kind
          if tok_type == tokenize.COMMENT:
              kind = 'comment'
          elif tok_type == tokenize.OP:
              kind = 'operator'
          elif tok_type == tokenize.STRING:
              kind = 'string'
              if prev_tok_type == tokenize.INDENT or scol==0:
                  kind = 'docstring'
          elif tok_type == tokenize.NAME:
              if tok_str in ('def', 'class', 'import', 'from'):
                  kind = 'definition'
              elif prev_tok_str in ('def', 'class'):
                  kind = 'defname'
              elif keyword.iskeyword(tok_str):
                  kind = 'keyword'
              elif is_builtin(tok_str) and prev_tok_str != '.':
                  kind = 'builtin'
          if kind:
              actions.append(((srow, scol), (erow, ecol), kind))
  
      for (srow, scol), (erow, ecol), kind in reversed(actions):
          lines[erow-1] = insert(lines[erow-1], ecol, '</span>')
          lines[srow-1] = insert(lines[srow-1], scol, '<span class="%s">' % kind)
  
      lines.insert(0, '<pre class="python">\n')
      lines.append('</pre>\n')
      return ''.join(lines)
  
  default_css = {
      '.comment': '{color: crimson;}',
      '.string':  '{color: forestgreen;}',
      '.docstring': '{color: forestgreen; font-style:italic}',
      '.keyword': '{color: darkorange;}',
      '.builtin': '{color: purple;}',
      '.definition': '{color: darkorange; font-weight:bold;}',
      '.defname': '{color: blue;}',
      '.operator': '{color: brown;}',
  }
  
  default_html = '''\
  <html><head><style type="text/css">
  %s
  </style></head>
  <body>
  %s
  </body></html>
  '''
  
  def build_page(source, html=default_html, css=default_css):
      'Create a complete HTML page with colorized Python source code'
      css_str = ''.join(['%s %s\n' % item for item in default_css.items()])
      result = colorize(source)
      return html % (css_str, result)
  
  
  if __name__ == '__main__':
      import sys, argparse, webbrowser, os
  
      parser = argparse.ArgumentParser(
          description = 'Convert Python source code to colorized HTML')
      parser.add_argument('sourcefile', metavar = 'SOURCEFILE', nargs = 1,
              help = 'File containing Python sourcecode')
      parser.add_argument('-b', '--browser', action = 'store_true',
              help = 'launch a browser to show results')
      parser.add_argument('-s', '--standalone', action = 'store_true',
              help = 'show a standalone snippet rather than a complete webpage')
      args = parser.parse_args()
      if args.browser and args.standalone:
          parser.error('The -s/--standalone option is incompatible with '
                       'the -b/--browser option')
  
      sourcefile = args.sourcefile[0]
      with open(sourcefile) as f:
          page = f.read()
      html = colorize(page) if args.standalone else build_page(page)
      if args.browser:
          htmlfile = os.path.splitext(os.path.basename(sourcefile))[0] + '.html'
          with open(htmlfile, 'w') as f:
              f.write(html)
          webbrowser.open('file://' + os.path.abspath(htmlfile))
      else:
          sys.stdout.write(html)
  
subject: Add syntax highlighter tool