text: from __future__ import print_function
  from __future__ import unicode_literals
  import time
  from netmiko.cisco_base_connection import CiscoSSHConnection
  
  
  class CiscoXrSSH(CiscoSSHConnection):
  
      def session_preparation(self):
          """Prepare the session after the connection has been established."""
          self._test_channel_read()
          self.set_base_prompt()
          self.disable_paging()
          self.set_terminal_width(command='terminal width 511')
          # Clear the read buffer
          time.sleep(.3 * self.global_delay_factor)
          self.clear_buffer()
  
      def send_config_set(self, config_commands=None, exit_config_mode=True, **kwargs):
          """IOS-XR requires you not exit from configuration mode."""
          return super(CiscoXrSSH, self).send_config_set(config_commands=config_commands,
                                                         exit_config_mode=False, **kwargs)
  
      def commit(self, confirm=False, confirm_delay=None, comment='', label='', delay_factor=1):
          """
          Commit the candidate configuration.
  
          default (no options):
              command_string = commit
          confirm and confirm_delay:
              command_string = commit confirmed <confirm_delay>
          label (which is a label name):
              command_string = commit label <label>
          comment:
              command_string = commit comment <comment>
  
          supported combinations
          label and confirm:
              command_string = commit label <label> confirmed <confirm_delay>
          label and comment:
              command_string = commit label <label> comment <comment>
  
          All other combinations will result in an exception.
  
          failed commit message:
          % Failed to commit one or more configuration items during a pseudo-atomic operation. All
          changes made have been reverted. Please issue 'show configuration failed [inheritance]'
          from this session to view the errors
  
          message XR shows if other commits occurred:
          One or more commits have occurred from other configuration sessions since this session
          started or since the last commit was made from this session. You can use the 'show
          configuration commit changes' command to browse the changes.
  
          Exit of configuration mode with pending changes will cause the changes to be discarded and
          an exception to be generated.
          """
          delay_factor = self.select_delay_factor(delay_factor)
          if confirm and not confirm_delay:
              raise ValueError("Invalid arguments supplied to XR commit")
          if confirm_delay and not confirm:
              raise ValueError("Invalid arguments supplied to XR commit")
          if comment and confirm:
              raise ValueError("Invalid arguments supplied to XR commit")
  
          # wrap the comment in quotes
          if comment:
              if '"' in comment:
                  raise ValueError("Invalid comment contains double quote")
              comment = '"{0}"'.format(comment)
  
          label = str(label)
          error_marker = 'Failed to'
          alt_error_marker = 'One or more commits have occurred from other'
  
          # Select proper command string based on arguments provided
          if label:
              if comment:
                  command_string = 'commit label {0} comment {1}'.format(label, comment)
              elif confirm:
                  command_string = 'commit label {0} confirmed {1}'.format(label, str(confirm_delay))
              else:
                  command_string = 'commit label {0}'.format(label)
          elif confirm:
              command_string = 'commit confirmed {0}'.format(str(confirm_delay))
          elif comment:
              command_string = 'commit comment {0}'.format(comment)
          else:
              command_string = 'commit'
  
          # Enter config mode (if necessary)
          output = self.config_mode()
          output += self.send_command_expect(command_string, strip_prompt=False, strip_command=False,
                                             delay_factor=delay_factor)
          if error_marker in output:
              raise ValueError("Commit failed with the following errors:\n\n{0}".format(output))
          if alt_error_marker in output:
              # Other commits occurred, don't proceed with commit
              output += self.send_command_timing("no", strip_prompt=False, strip_command=False,
                                                 delay_factor=delay_factor)
              raise ValueError("Commit failed with the following errors:\n\n{0}".format(output))
  
          return output
  
      def check_config_mode(self, check_string=')#', pattern=r"[#\$]"):
          """Checks if the device is in configuration mode or not.
  
          IOS-XR, unfortunately, does this:
          RP/0/RSP0/CPU0:BNG(admin)#
          """
          self.write_channel(self.RETURN)
          output = self.read_until_pattern(pattern=pattern)
          # Strip out (admin) so we don't get a false positive with (admin)#
          # (admin-config)# would still match.
          output = output.replace("(admin)", "")
          return check_string in output
  
      def exit_config_mode(self, exit_config='end'):
          """Exit configuration mode."""
          output = ''
          if self.check_config_mode():
              output = self.send_command_timing(exit_config, strip_prompt=False, strip_command=False)
              if "Uncommitted changes found" in output:
                  output += self.send_command_timing('no', strip_prompt=False, strip_command=False)
              if self.check_config_mode():
                  raise ValueError("Failed to exit configuration mode")
          return output
  
      def save_config(self):
          """Not Implemented (use commit() method)"""
          raise NotImplementedError
  