mirror of
https://github.com/ets-labs/python-dependency-injector.git
synced 2024-11-27 03:54:00 +03:00
334 lines
9.4 KiB
Python
334 lines
9.4 KiB
Python
"""Providers module."""
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from six import class_types
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from .utils import ensure_is_provider
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from .utils import is_kwarg_injection
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from .utils import is_attribute_injection
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from .utils import is_method_injection
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from .errors import Error
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class Provider(object):
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"""Base provider class."""
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__IS_OBJECTS_PROVIDER__ = True
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__slots__ = ('overridden',)
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def __init__(self):
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"""Initializer."""
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self.overridden = None
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def __call__(self, *args, **kwargs):
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"""Return provided instance."""
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if self.overridden:
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return self.last_overriding(*args, **kwargs)
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return self._provide(*args, **kwargs)
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def _provide(self, *args, **kwargs):
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"""Providing strategy implementation.
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Abstract protected method that implements providing strategy of
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particular provider. Current method is called every time when not
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overridden provider is called. Need to be overridden in subclasses.
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"""
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raise NotImplementedError()
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def delegate(self):
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"""Return provider's delegate."""
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return Delegate(self)
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def override(self, provider):
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"""Override provider with another provider."""
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if not self.overridden:
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self.overridden = (ensure_is_provider(provider),)
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else:
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self.overridden = self.overridden + (ensure_is_provider(provider),)
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@property
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def last_overriding(self):
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"""Return last overriding provider."""
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try:
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return self.overridden[-1]
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except (TypeError, IndexError):
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raise Error('Provider {0} is not overridden'.format(str(self)))
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def reset_last_overriding(self):
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"""Reset last overriding provider."""
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if not self.overridden:
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raise Error('Provider {0} is not overridden'.format(str(self)))
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self.overridden = self.overridden[:-1]
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def reset_override(self):
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"""Reset all overriding providers."""
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self.overridden = None
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class Delegate(Provider):
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"""Provider's delegate."""
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__slots__ = ('delegated',)
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def __init__(self, delegated):
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"""Initializer.
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:type delegated: Provider
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"""
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self.delegated = ensure_is_provider(delegated)
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super(Delegate, self).__init__()
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def _provide(self, *args, **kwargs):
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"""Return provided instance."""
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return self.delegated
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class Factory(Provider):
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"""Factory provider.
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Factory provider creates new instance of specified class on every call.
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"""
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__slots__ = ('provides', 'kwargs', 'attributes', 'methods')
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def __init__(self, provides, *injections):
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"""Initializer."""
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if not isinstance(provides, class_types):
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raise Error('Factory provider expects to get class, ' +
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'got {0} instead'.format(str(provides)))
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self.provides = provides
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self.kwargs = tuple((injection
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for injection in injections
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if is_kwarg_injection(injection)))
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self.attributes = tuple((injection
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for injection in injections
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if is_attribute_injection(injection)))
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self.methods = tuple((injection
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for injection in injections
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if is_method_injection(injection)))
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super(Factory, self).__init__()
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def _provide(self, *args, **kwargs):
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"""Return provided instance."""
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init_kwargs = dict(((injection.name, injection.value)
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for injection in self.kwargs))
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init_kwargs.update(kwargs)
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instance = self.provides(*args, **init_kwargs)
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for attribute in self.attributes:
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setattr(instance, attribute.name, attribute.value)
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for method in self.methods:
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getattr(instance, method.name)(method.value)
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return instance
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class NewInstance(Factory):
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"""NewInstance provider.
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It is synonym of Factory provider. NewInstance provider is considered to
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be deprecated, but will be able to use for further backward
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compatibility.
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"""
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class Singleton(Provider):
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"""Singleton provider.
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Singleton provider will create instance once and return it on every call.
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"""
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__slots__ = ('instance', 'factory')
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def __init__(self, *args, **kwargs):
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"""Initializer."""
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self.instance = None
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self.factory = Factory(*args, **kwargs)
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super(Singleton, self).__init__()
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def _provide(self, *args, **kwargs):
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"""Return provided instance."""
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if not self.instance:
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self.instance = self.factory(*args, **kwargs)
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return self.instance
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def reset(self):
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"""Reset instance."""
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self.instance = None
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class ExternalDependency(Provider):
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"""External dependency provider.
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Those provider is used when dependency obviously have to be overridden by
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the client's code, but it's interface is known.
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"""
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__slots__ = ('instance_of',)
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def __init__(self, instance_of):
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"""Initializer."""
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if not isinstance(instance_of, class_types):
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raise Error('ExternalDependency provider expects to get class, ' +
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'got {0} instead'.format(str(instance_of)))
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self.instance_of = instance_of
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super(ExternalDependency, self).__init__()
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def __call__(self, *args, **kwargs):
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"""Return provided instance."""
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if not self.overridden:
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raise Error('Dependency is not defined')
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instance = self.last_overriding(*args, **kwargs)
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if not isinstance(instance, self.instance_of):
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raise Error('{0} is not an '.format(instance) +
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'instance of {0}'.format(self.instance_of))
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return instance
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def provided_by(self, provider):
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"""Set external dependency provider."""
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return self.override(provider)
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class _StaticProvider(Provider):
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"""Static provider.
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Static provider is base implementation that provides exactly the same as
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it got on input.
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"""
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__slots__ = ('provides',)
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def __init__(self, provides):
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"""Initializer."""
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self.provides = provides
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super(_StaticProvider, self).__init__()
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def _provide(self, *args, **kwargs):
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"""Return provided instance."""
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return self.provides
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class Class(_StaticProvider):
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"""Class provider provides class."""
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class Object(_StaticProvider):
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"""Object provider provides object."""
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class Function(_StaticProvider):
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"""Function provider provides function."""
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class Value(_StaticProvider):
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"""Value provider provides value."""
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class Callable(Provider):
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"""Callable provider.
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Callable provider provides callable that is called on every provider call
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with some predefined dependency injections.
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"""
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__slots__ = ('callback', 'injections')
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def __init__(self, callback, *injections):
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"""Initializer."""
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if not callable(callback):
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raise Error('Callable expected, got {0}'.format(str(callback)))
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self.callback = callback
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self.injections = tuple((injection
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for injection in injections
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if is_kwarg_injection(injection)))
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super(Callable, self).__init__()
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def _provide(self, *args, **kwargs):
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"""Return provided instance."""
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injections = dict(((injection.name, injection.value)
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for injection in self.injections))
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injections.update(kwargs)
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return self.callback(*args, **injections)
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class Config(Provider):
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"""Config provider.
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Config provider provides dict values. Also config provider creates
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child config objects for all undefined attribute calls. It makes possible
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to create deferred config value provider.
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"""
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__slots__ = ('value',)
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def __init__(self, value=None):
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"""Initializer."""
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if not value:
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value = dict()
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self.value = value
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super(Config, self).__init__()
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def __getattr__(self, item):
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"""Return instance of deferred config."""
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return _ChildConfig(parents=(item,), root_config=self)
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def _provide(self, paths=None):
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"""Return provided instance."""
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value = self.value
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if paths:
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for path in paths:
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try:
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value = value[path]
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except KeyError:
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raise Error('Config key '
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'"{0}" is undefined'.format('.'.join(paths)))
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return value
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def update_from(self, value):
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"""Update current value from another one."""
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self.value.update(value)
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class _ChildConfig(Provider):
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"""Child config provider.
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Child config provide an value from the root config object according to
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the current path in the config tree.
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"""
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__slots__ = ('parents', 'root_config')
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def __init__(self, parents, root_config):
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"""Initializer."""
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self.parents = parents
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self.root_config = root_config
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super(_ChildConfig, self).__init__()
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def __getattr__(self, item):
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"""Return instance of deferred config."""
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return _ChildConfig(parents=self.parents + (item,),
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root_config=self.root_config)
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def _provide(self, *args, **kwargs):
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"""Return provided instance."""
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return self.root_config(self.parents)
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