/usr/lib/python3/dist-packages/cement/ext/ext_yaml.py is in python3-cement 2.10.0-1.
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The Yaml Extension adds the :class:`YamlOutputHandler` to render
output in pure Yaml, as well as the :class:`YamlConfigHandler` that allows
applications to use Yaml configuration files as a drop-in replacement of
the default :class:`cement.ext.ext_configparser.ConfigParserConfigHandler`.
Requirements
------------
* pyYaml (``pip install pyYaml``)
Configuration
-------------
This extension does not honor any application configuration settings.
Usage
_____
**myapp.conf**
.. code-block:: Yaml
---
myapp:
foo: bar
**myapp.py**
.. code-block:: python
from cement.core.foundation import CementApp
class MyApp(CementApp):
class Meta:
label = 'myapp'
extensions = ['Yaml']
config_handler = 'Yaml'
# you probably don't want to do this.. but you can
# output_handler = 'Yaml'
with MyApp() as app:
app.run()
# create some data
data = dict(foo=app.config.get('myapp', 'foo'))
app.render(data)
In general, you likely would not set ``output_handler`` to ``Yaml``, but
rather another type of output handler that displays readable output to the
end-user (i.e. Mustache, Genshi, or Tabulate). By default Cement
adds the ``-o`` command line option to allow the end user to override the
output handler. For example: passing ``-o Yaml`` will override the default
output handler and set it to ``YamlOutputHandler``.
See ``CementApp.Meta.handler_override_options``.
.. code-block:: console
$ python myapp.py -o Yaml
{foo: bar}
"""
import yaml
from ..core import output
from ..utils.misc import minimal_logger
from ..ext.ext_configparser import ConfigParserConfigHandler
LOG = minimal_logger(__name__)
def suppress_output_before_run(app):
"""
This is a ``post_argument_parsing`` hook that suppresses console output if
the ``YamlOutputHandler`` is triggered via command line.
:param app: The application object.
"""
if not hasattr(app.pargs, 'output_handler_override'):
return
elif app.pargs.output_handler_override == 'yaml':
app._suppress_output()
def unsuppress_output_before_render(app, data):
"""
This is a ``pre_render`` that unsuppresses console output if
the ``YamlOutputHandler`` is triggered via command line so that the Yaml
is the only thing in the output.
:param app: The application object.
"""
if not hasattr(app.pargs, 'output_handler_override'):
return
elif app.pargs.output_handler_override == 'yaml':
app._unsuppress_output()
def suppress_output_after_render(app, out_text):
"""
This is a ``post_render`` hook that suppresses console output again after
rendering, only if the ``YamlOutputHandler`` is triggered via command
line.
:param app: The application object.
"""
if not hasattr(app.pargs, 'output_handler_override'):
return
elif app.pargs.output_handler_override == 'yaml':
app._suppress_output()
class YamlOutputHandler(output.CementOutputHandler):
"""
This class implements the :ref:`IOutput <cement.core.output>`
interface. It provides Yaml output from a data dictionary and uses
`pyYaml <http://pyYaml.org/wiki/PyYamlDocumentation>`_ to dump it to
STDOUT. Please see the developer documentation on
:ref:`Output Handling <dev_output_handling>`.
This handler forces Cement to suppress console output until
``app.render`` is called (keeping the output pure Yaml). If
troubleshooting issues, you will need to pass the ``--debug`` option in
order to unsuppress output and see what's happening.
"""
class Meta:
"""Handler meta-data."""
interface = output.IOutput
label = 'yaml'
#: Whether or not to include ``Yaml`` as an available to choice
#: to override the ``output_handler`` via command line options.
overridable = True
def __init__(self, *args, **kw):
super(YamlOutputHandler, self).__init__(*args, **kw)
self.config = None
def _setup(self, app_obj):
self.app = app_obj
def render(self, data_dict, template=None, **kw):
"""
Take a data dictionary and render it as Yaml output. Note that the
template option is received here per the interface, however this
handler just ignores it. Additional keyword arguments passed to
``yaml.dump()``.
:param data_dict: The data dictionary to render.
:keyword template: Ignored in this output handler implementation.
:returns: A Yaml encoded string.
:rtype: ``str``
"""
LOG.debug("rendering output as yaml via %s" % self.__module__)
return yaml.dump(data_dict, **kw)
class YamlConfigHandler(ConfigParserConfigHandler):
"""
This class implements the :ref:`IConfig <cement.core.config>`
interface, and provides the same functionality of
:ref:`ConfigParserConfigHandler <cement.ext.ext_configparser>`
but with Yaml configuration files. See
`pyYaml <http://pyYaml.org/wiki/PyYamlDocumentation>`_ for more
information on pyYaml.
**Note** This extension has an external dependency on `pyYaml`. You must
include `pyYaml` in your application's dependencies as Cement explicitly
does *not* include external dependencies for optional extensions.
"""
class Meta:
label = 'yaml'
def __init__(self, *args, **kw):
super(YamlConfigHandler, self).__init__(*args, **kw)
def _parse_file(self, file_path):
"""
Parse Yaml configuration file settings from file_path, overwriting
existing config settings. If the file does not exist, returns False.
:param file_path: The file system path to the Yaml configuration file.
:returns: boolean
"""
self.merge(yaml.load(open(file_path)))
# FIX ME: Should check that file was read properly, however if not it
# will likely raise an exception anyhow.
return True
def load(app):
app.hook.register('post_argument_parsing', suppress_output_before_run)
app.hook.register('pre_render', unsuppress_output_before_render)
app.hook.register('post_render', suppress_output_after_render)
app.handler.register(YamlOutputHandler)
app.handler.register(YamlConfigHandler)
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