code: def workon_cmd(argv):
      
      parser = argparse.ArgumentParser(prog='pew workon')
      parser.add_argument('envname', nargs='?')
      parser.add_argument(
          '-n', '--no-cd', action='store_true',
          help=('Do not change working directory to project directory after '
                'activating virtualenv.')
      )
      args = parser.parse_args(argv)
  
      def list_and_exit():
          lsvirtualenv(False)
          sys.exit(0)
  
      env = parse_envname([args.envname], list_and_exit)
  
      # Check if the virtualenv has an associated project directory and in
      # this case, use it as the current working directory.
      project_dir = get_project_dir(env)
      if project_dir is None or args.no_cd:
          project_dir = os.getcwd()
  
      return shell(env, cwd=project_dir)
docs: List or change working virtual environments.