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"""Application base class for displaying data.
"""
import abc
import logging
import stevedore
from .command import Command
LOG = logging.getLogger(__name__)
class DisplayCommandBase(Command):
"""Command base class for displaying data about a single object.
"""
__metaclass__ = abc.ABCMeta
def __init__(self, app, app_args):
super(DisplayCommandBase, self).__init__(app, app_args)
self.formatters = self._load_formatter_plugins()
@abc.abstractproperty
def formatter_namespace(self):
"String specifying the namespace to use for loading formatter plugins."
@abc.abstractproperty
def formatter_default(self):
"String specifying the name of the default formatter."
def _load_formatter_plugins(self):
# Here so tests can override
return stevedore.ExtensionManager(
self.formatter_namespace,
invoke_on_load=True,
)
def get_parser(self, prog_name):
parser = super(DisplayCommandBase, self).get_parser(prog_name)
formatter_group = parser.add_argument_group(
title='output formatters',
description='output formatter options',
)
formatter_choices = sorted(self.formatters.names())
formatter_default = self.formatter_default
if formatter_default not in formatter_choices:
formatter_default = formatter_choices[0]
formatter_group.add_argument(
'-f', '--format',
dest='formatter',
action='store',
choices=formatter_choices,
default=formatter_default,
help='the output format, defaults to %s' % formatter_default,
)
formatter_group.add_argument(
'-c', '--column',
action='append',
default=[],
dest='columns',
metavar='COLUMN',
help='specify the column(s) to include, can be repeated',
)
for formatter in self.formatters:
formatter.obj.add_argument_group(parser)
return parser
@abc.abstractmethod
def produce_output(self, parsed_args, column_names, data):
"""Use the formatter to generate the output.
:param parsed_args: argparse.Namespace instance with argument values
:param column_names: sequence of strings containing names
of output columns
:param data: iterable with values matching the column names
"""
def run(self, parsed_args):
self.formatter = self.formatters[parsed_args.formatter].obj
column_names, data = self.take_action(parsed_args)
self.produce_output(parsed_args, column_names, data)
return 0
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