old_contents: #!/usr/bin/env python
  # -*- coding:utf-8 -*-
  
  """
  .. note:: This module is not designed to be used by user.
  """
  
  import collections
  import weakref
  
  
  class RuntimePath(collections.MutableSequence):
      def __init__(self, vim):
          """
          :param vim: ``Vim`` object which owns this object.
          :type vim: Vim
          """
          self._ref = weakref.ref(vim)
          self._list = self.parse(vim.command('set runtimepath'))
  
      def __str__(self):
          return self.format(self._list)
  
      def __repr__(self):
          return self._list.__repr__()
  
      def __len__(self):
          return self._list.__len__()
  
      def __getitem__(self, key):
          return self._list.__getitem__(key)
  
      def __setitem__(self, key, value):
          self._list.__setitem__(key, value)
          self._sync()
  
      def __delitem__(self, key):
          self._list.__delitem__(key)
          self._sync()
  
      def insert(self, index, value):
          """
          Insert object before index.
  
          :param int index: index to insert in
          :param string value: path to insert
          """
          self._list.insert(index, value)
          self._sync()
  
      def format(self, list):
          """
          Format list to runtime path representation.
  
          :param list: list of paths to format
          :type list: list of string
          :return: *Vim* style runtime path string representation
          :rtype: string
          """
          values = ','.join(list)
          return 'runtimepath=' + values
  
      def parse(self, string):
          """
          Parse runtime path representation to list.
  
          :param string string: runtime path string
          :return: list of runtime paths
          :rtype: list of string
          """
          var, eq, values = string.strip().partition('=')
          assert var == 'runtimepath'
          assert eq == '='
          return values.split(',')
  
      def _sync(self):
          vim = self._ref()
          if vim:
              vim.command('set {0}'.format(str(self)), False)
  
new_contents: #!/usr/bin/env python
  # -*- coding:utf-8 -*-
  
  """
  .. note:: This module is not designed to be used by user.
  """
  
  import collections
  import weakref
  
  
  class RuntimePath(collections.MutableSequence):
      def __init__(self, vim):
          """
          :param vim: ``Vim`` object which owns this object.
          :type vim: Vim
          """
          self._ref = weakref.ref(vim)
          self._list = self.parse(vim.command('set runtimepath'))
  
      def __str__(self):
          return self.format(self._list)
  
      def __repr__(self):
          return self._list.__repr__()
  
      def __len__(self):
          return self._list.__len__()
  
      def __getitem__(self, key):
          return self._list.__getitem__(key)
  
      def __setitem__(self, key, value):
          self._list.__setitem__(key, value)
          self._sync()
  
      def __delitem__(self, key):
          self._list.__delitem__(key)
          self._sync()
  
      def insert(self, index, value):
          """
          Insert object before index.
  
          :param int index: index to insert in
          :param string value: path to insert
          """
          self._list.insert(index, value)
          self._sync()
  
      def format(self, list):
          """
          Format list to runtime path representation.
  
          :param list: list of paths to format
          :type list: list of string
          :return: *Vim* style runtime path string representation
          :rtype: string
          """
          values = ','.join(list)
          return 'runtimepath=' + values
  
      def parse(self, string):
          """
          Parse runtime path representation to list.
  
          :param string string: runtime path string
          :return: list of runtime paths
          :rtype: list of string
          """
          var, eq, values = string.strip().partition('=')
          assert var == 'runtimepath'
          assert eq == '='
          return values.split(',')
  
      def _sync(self):
          vim = self._ref()
          if vim:
              vim.command('set {0!s}'.format(self), False)
  
subject: use {0!s} instread of str()