/usr/lib/python2.7/dist-packages/traitlets/config/configurable.py is in python-traitlets 4.3.1-1.
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"""A base class for objects that are configurable."""
# Copyright (c) IPython Development Team.
# Distributed under the terms of the Modified BSD License.
from __future__ import print_function, absolute_import
from copy import deepcopy
import warnings
from .loader import Config, LazyConfigValue, _is_section_key
from traitlets.traitlets import HasTraits, Instance, observe, observe_compat, default
from ipython_genutils.text import indent, dedent, wrap_paragraphs
#-----------------------------------------------------------------------------
# Helper classes for Configurables
#-----------------------------------------------------------------------------
class ConfigurableError(Exception):
pass
class MultipleInstanceError(ConfigurableError):
pass
#-----------------------------------------------------------------------------
# Configurable implementation
#-----------------------------------------------------------------------------
class Configurable(HasTraits):
config = Instance(Config, (), {})
parent = Instance('traitlets.config.configurable.Configurable', allow_none=True)
def __init__(self, **kwargs):
"""Create a configurable given a config config.
Parameters
----------
config : Config
If this is empty, default values are used. If config is a
:class:`Config` instance, it will be used to configure the
instance.
parent : Configurable instance, optional
The parent Configurable instance of this object.
Notes
-----
Subclasses of Configurable must call the :meth:`__init__` method of
:class:`Configurable` *before* doing anything else and using
:func:`super`::
class MyConfigurable(Configurable):
def __init__(self, config=None):
super(MyConfigurable, self).__init__(config=config)
# Then any other code you need to finish initialization.
This ensures that instances will be configured properly.
"""
parent = kwargs.pop('parent', None)
if parent is not None:
# config is implied from parent
if kwargs.get('config', None) is None:
kwargs['config'] = parent.config
self.parent = parent
config = kwargs.pop('config', None)
# load kwarg traits, other than config
super(Configurable, self).__init__(**kwargs)
# load config
if config is not None:
# We used to deepcopy, but for now we are trying to just save
# by reference. This *could* have side effects as all components
# will share config. In fact, I did find such a side effect in
# _config_changed below. If a config attribute value was a mutable type
# all instances of a component were getting the same copy, effectively
# making that a class attribute.
# self.config = deepcopy(config)
self.config = config
else:
# allow _config_default to return something
self._load_config(self.config)
# Ensure explicit kwargs are applied after loading config.
# This is usually redundant, but ensures config doesn't override
# explicitly assigned values.
for key, value in kwargs.items():
setattr(self, key, value)
#-------------------------------------------------------------------------
# Static trait notifiations
#-------------------------------------------------------------------------
@classmethod
def section_names(cls):
"""return section names as a list"""
return [c.__name__ for c in reversed(cls.__mro__) if
issubclass(c, Configurable) and issubclass(cls, c)
]
def _find_my_config(self, cfg):
"""extract my config from a global Config object
will construct a Config object of only the config values that apply to me
based on my mro(), as well as those of my parent(s) if they exist.
If I am Bar and my parent is Foo, and their parent is Tim,
this will return merge following config sections, in this order::
[Bar, Foo.bar, Tim.Foo.Bar]
With the last item being the highest priority.
"""
cfgs = [cfg]
if self.parent:
cfgs.append(self.parent._find_my_config(cfg))
my_config = Config()
for c in cfgs:
for sname in self.section_names():
# Don't do a blind getattr as that would cause the config to
# dynamically create the section with name Class.__name__.
if c._has_section(sname):
my_config.merge(c[sname])
return my_config
def _load_config(self, cfg, section_names=None, traits=None):
"""load traits from a Config object"""
if traits is None:
traits = self.traits(config=True)
if section_names is None:
section_names = self.section_names()
my_config = self._find_my_config(cfg)
# hold trait notifications until after all config has been loaded
with self.hold_trait_notifications():
for name, config_value in my_config.items():
if name in traits:
if isinstance(config_value, LazyConfigValue):
# ConfigValue is a wrapper for using append / update on containers
# without having to copy the initial value
initial = getattr(self, name)
config_value = config_value.get_value(initial)
# We have to do a deepcopy here if we don't deepcopy the entire
# config object. If we don't, a mutable config_value will be
# shared by all instances, effectively making it a class attribute.
setattr(self, name, deepcopy(config_value))
elif not _is_section_key(name) and not isinstance(config_value, Config):
from difflib import get_close_matches
if isinstance(self, LoggingConfigurable):
warn = self.log.warning
else:
warn = lambda msg: warnings.warn(msg, stacklevel=9)
matches = get_close_matches(name, traits)
msg = u"Config option `{option}` not recognized by `{klass}`.".format(
option=name, klass=self.__class__.__name__)
if len(matches) == 1:
msg += u" Did you mean `{matches}`?".format(matches=matches[0])
elif len(matches) >= 1:
msg +=" Did you mean one of: `{matches}`?".format(matches=', '.join(sorted(matches)))
warn(msg)
@observe('config')
@observe_compat
def _config_changed(self, change):
"""Update all the class traits having ``config=True`` in metadata.
For any class trait with a ``config`` metadata attribute that is
``True``, we update the trait with the value of the corresponding
config entry.
"""
# Get all traits with a config metadata entry that is True
traits = self.traits(config=True)
# We auto-load config section for this class as well as any parent
# classes that are Configurable subclasses. This starts with Configurable
# and works down the mro loading the config for each section.
section_names = self.section_names()
self._load_config(change.new, traits=traits, section_names=section_names)
def update_config(self, config):
"""Update config and load the new values"""
# traitlets prior to 4.2 created a copy of self.config in order to trigger change events.
# Some projects (IPython < 5) relied upon one side effect of this,
# that self.config prior to update_config was not modified in-place.
# For backward-compatibility, we must ensure that self.config
# is a new object and not modified in-place,
# but config consumers should not rely on this behavior.
self.config = deepcopy(self.config)
# load config
self._load_config(config)
# merge it into self.config
self.config.merge(config)
# TODO: trigger change event if/when dict-update change events take place
# DO NOT trigger full trait-change
@classmethod
def class_get_help(cls, inst=None):
"""Get the help string for this class in ReST format.
If `inst` is given, it's current trait values will be used in place of
class defaults.
"""
assert inst is None or isinstance(inst, cls)
final_help = []
final_help.append(u'%s options' % cls.__name__)
final_help.append(len(final_help[0])*u'-')
for k, v in sorted(cls.class_traits(config=True).items()):
help = cls.class_get_trait_help(v, inst)
final_help.append(help)
return '\n'.join(final_help)
@classmethod
def class_get_trait_help(cls, trait, inst=None):
"""Get the help string for a single trait.
If `inst` is given, it's current trait values will be used in place of
the class default.
"""
assert inst is None or isinstance(inst, cls)
lines = []
header = "--%s.%s=<%s>" % (cls.__name__, trait.name, trait.__class__.__name__)
lines.append(header)
if inst is not None:
lines.append(indent('Current: %r' % getattr(inst, trait.name), 4))
else:
try:
dvr = trait.default_value_repr()
except Exception:
dvr = None # ignore defaults we can't construct
if dvr is not None:
if len(dvr) > 64:
dvr = dvr[:61]+'...'
lines.append(indent('Default: %s' % dvr, 4))
if 'Enum' in trait.__class__.__name__:
# include Enum choices
lines.append(indent('Choices: %r' % (trait.values,)))
help = trait.help
if help != '':
help = '\n'.join(wrap_paragraphs(help, 76))
lines.append(indent(help, 4))
return '\n'.join(lines)
@classmethod
def class_print_help(cls, inst=None):
"""Get the help string for a single trait and print it."""
print(cls.class_get_help(inst))
@classmethod
def class_config_section(cls):
"""Get the config class config section"""
def c(s):
"""return a commented, wrapped block."""
s = '\n\n'.join(wrap_paragraphs(s, 78))
return '## ' + s.replace('\n', '\n# ')
# section header
breaker = '#' + '-'*78
parent_classes = ','.join(p.__name__ for p in cls.__bases__)
s = "# %s(%s) configuration" % (cls.__name__, parent_classes)
lines = [breaker, s, breaker, '']
# get the description trait
desc = cls.class_traits().get('description')
if desc:
desc = desc.default_value
if not desc:
# no description from trait, use __doc__
desc = getattr(cls, '__doc__', '')
if desc:
lines.append(c(desc))
lines.append('')
for name, trait in sorted(cls.class_own_traits(config=True).items()):
lines.append(c(trait.help))
lines.append('#c.%s.%s = %s' % (cls.__name__, name, trait.default_value_repr()))
lines.append('')
return '\n'.join(lines)
@classmethod
def class_config_rst_doc(cls):
"""Generate rST documentation for this class' config options.
Excludes traits defined on parent classes.
"""
lines = []
classname = cls.__name__
for k, trait in sorted(cls.class_own_traits(config=True).items()):
ttype = trait.__class__.__name__
termline = classname + '.' + trait.name
# Choices or type
if 'Enum' in ttype:
# include Enum choices
termline += ' : ' + '|'.join(repr(x) for x in trait.values)
else:
termline += ' : ' + ttype
lines.append(termline)
# Default value
try:
dvr = trait.default_value_repr()
except Exception:
dvr = None # ignore defaults we can't construct
if dvr is not None:
if len(dvr) > 64:
dvr = dvr[:61]+'...'
# Double up backslashes, so they get to the rendered docs
dvr = dvr.replace('\\n', '\\\\n')
lines.append(' Default: ``%s``' % dvr)
lines.append('')
help = trait.help or 'No description'
lines.append(indent(dedent(help), 4))
# Blank line
lines.append('')
return '\n'.join(lines)
class LoggingConfigurable(Configurable):
"""A parent class for Configurables that log.
Subclasses have a log trait, and the default behavior
is to get the logger from the currently running Application.
"""
log = Instance('logging.Logger')
@default('log')
def _log_default(self):
from traitlets import log
return log.get_logger()
class SingletonConfigurable(LoggingConfigurable):
"""A configurable that only allows one instance.
This class is for classes that should only have one instance of itself
or *any* subclass. To create and retrieve such a class use the
:meth:`SingletonConfigurable.instance` method.
"""
_instance = None
@classmethod
def _walk_mro(cls):
"""Walk the cls.mro() for parent classes that are also singletons
For use in instance()
"""
for subclass in cls.mro():
if issubclass(cls, subclass) and \
issubclass(subclass, SingletonConfigurable) and \
subclass != SingletonConfigurable:
yield subclass
@classmethod
def clear_instance(cls):
"""unset _instance for this class and singleton parents.
"""
if not cls.initialized():
return
for subclass in cls._walk_mro():
if isinstance(subclass._instance, cls):
# only clear instances that are instances
# of the calling class
subclass._instance = None
@classmethod
def instance(cls, *args, **kwargs):
"""Returns a global instance of this class.
This method create a new instance if none have previously been created
and returns a previously created instance is one already exists.
The arguments and keyword arguments passed to this method are passed
on to the :meth:`__init__` method of the class upon instantiation.
Examples
--------
Create a singleton class using instance, and retrieve it::
>>> from traitlets.config.configurable import SingletonConfigurable
>>> class Foo(SingletonConfigurable): pass
>>> foo = Foo.instance()
>>> foo == Foo.instance()
True
Create a subclass that is retrived using the base class instance::
>>> class Bar(SingletonConfigurable): pass
>>> class Bam(Bar): pass
>>> bam = Bam.instance()
>>> bam == Bar.instance()
True
"""
# Create and save the instance
if cls._instance is None:
inst = cls(*args, **kwargs)
# Now make sure that the instance will also be returned by
# parent classes' _instance attribute.
for subclass in cls._walk_mro():
subclass._instance = inst
if isinstance(cls._instance, cls):
return cls._instance
else:
raise MultipleInstanceError(
'Multiple incompatible subclass instances of '
'%s are being created.' % cls.__name__
)
@classmethod
def initialized(cls):
"""Has an instance been created?"""
return hasattr(cls, "_instance") and cls._instance is not None
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