262 lines
7.5 KiB
Python
262 lines
7.5 KiB
Python
# orm/path_registry.py
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# Copyright (C) 2005-2014 the SQLAlchemy authors and contributors <see AUTHORS file>
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#
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# This module is part of SQLAlchemy and is released under
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# the MIT License: http://www.opensource.org/licenses/mit-license.php
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"""Path tracking utilities, representing mapper graph traversals.
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"""
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from .. import inspection
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from .. import util
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from .. import exc
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from itertools import chain
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from .base import class_mapper
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def _unreduce_path(path):
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return PathRegistry.deserialize(path)
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_WILDCARD_TOKEN = "*"
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_DEFAULT_TOKEN = "_sa_default"
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class PathRegistry(object):
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"""Represent query load paths and registry functions.
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Basically represents structures like:
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(<User mapper>, "orders", <Order mapper>, "items", <Item mapper>)
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These structures are generated by things like
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query options (joinedload(), subqueryload(), etc.) and are
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used to compose keys stored in the query._attributes dictionary
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for various options.
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They are then re-composed at query compile/result row time as
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the query is formed and as rows are fetched, where they again
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serve to compose keys to look up options in the context.attributes
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dictionary, which is copied from query._attributes.
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The path structure has a limited amount of caching, where each
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"root" ultimately pulls from a fixed registry associated with
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the first mapper, that also contains elements for each of its
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property keys. However paths longer than two elements, which
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are the exception rather than the rule, are generated on an
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as-needed basis.
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"""
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def __eq__(self, other):
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return other is not None and \
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self.path == other.path
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def set(self, attributes, key, value):
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attributes[(key, self.path)] = value
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def setdefault(self, attributes, key, value):
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attributes.setdefault((key, self.path), value)
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def get(self, attributes, key, value=None):
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key = (key, self.path)
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if key in attributes:
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return attributes[key]
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else:
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return value
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def __len__(self):
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return len(self.path)
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@property
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def length(self):
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return len(self.path)
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def pairs(self):
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path = self.path
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for i in range(0, len(path), 2):
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yield path[i], path[i + 1]
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def contains_mapper(self, mapper):
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for path_mapper in [
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self.path[i] for i in range(0, len(self.path), 2)
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]:
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if path_mapper.is_mapper and \
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path_mapper.isa(mapper):
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return True
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else:
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return False
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def contains(self, attributes, key):
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return (key, self.path) in attributes
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def __reduce__(self):
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return _unreduce_path, (self.serialize(), )
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def serialize(self):
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path = self.path
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return list(zip(
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[m.class_ for m in [path[i] for i in range(0, len(path), 2)]],
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[path[i].key for i in range(1, len(path), 2)] + [None]
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))
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@classmethod
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def deserialize(cls, path):
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if path is None:
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return None
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p = tuple(chain(*[(class_mapper(mcls),
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class_mapper(mcls).attrs[key]
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if key is not None else None)
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for mcls, key in path]))
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if p and p[-1] is None:
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p = p[0:-1]
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return cls.coerce(p)
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@classmethod
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def per_mapper(cls, mapper):
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return EntityRegistry(
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cls.root, mapper
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)
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@classmethod
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def coerce(cls, raw):
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return util.reduce(lambda prev, next: prev[next], raw, cls.root)
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def token(self, token):
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if token.endswith(':' + _WILDCARD_TOKEN):
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return TokenRegistry(self, token)
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elif token.endswith(":" + _DEFAULT_TOKEN):
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return TokenRegistry(self.root, token)
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else:
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raise exc.ArgumentError("invalid token: %s" % token)
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def __add__(self, other):
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return util.reduce(
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lambda prev, next: prev[next],
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other.path, self)
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def __repr__(self):
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return "%s(%r)" % (self.__class__.__name__, self.path, )
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class RootRegistry(PathRegistry):
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"""Root registry, defers to mappers so that
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paths are maintained per-root-mapper.
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"""
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path = ()
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has_entity = False
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def __getitem__(self, entity):
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return entity._path_registry
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PathRegistry.root = RootRegistry()
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class TokenRegistry(PathRegistry):
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def __init__(self, parent, token):
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self.token = token
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self.parent = parent
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self.path = parent.path + (token,)
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has_entity = False
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def __getitem__(self, entity):
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raise NotImplementedError()
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class PropRegistry(PathRegistry):
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def __init__(self, parent, prop):
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# restate this path in terms of the
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# given MapperProperty's parent.
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insp = inspection.inspect(parent[-1])
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if not insp.is_aliased_class or insp._use_mapper_path:
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parent = parent.parent[prop.parent]
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elif insp.is_aliased_class and insp.with_polymorphic_mappers:
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if prop.parent is not insp.mapper and \
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prop.parent in insp.with_polymorphic_mappers:
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subclass_entity = parent[-1]._entity_for_mapper(prop.parent)
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parent = parent.parent[subclass_entity]
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self.prop = prop
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self.parent = parent
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self.path = parent.path + (prop,)
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@util.memoized_property
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def has_entity(self):
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return hasattr(self.prop, "mapper")
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@util.memoized_property
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def entity(self):
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return self.prop.mapper
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@util.memoized_property
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def _wildcard_path_loader_key(self):
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"""Given a path (mapper A, prop X), replace the prop with the wildcard,
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e.g. (mapper A, 'relationship:.*') or (mapper A, 'column:.*'), then
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return within the ("loader", path) structure.
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"""
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return ("loader",
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self.parent.token(
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"%s:%s" % (self.prop.strategy_wildcard_key, _WILDCARD_TOKEN)
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).path
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)
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@util.memoized_property
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def _default_path_loader_key(self):
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return ("loader",
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self.parent.token(
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"%s:%s" % (self.prop.strategy_wildcard_key, _DEFAULT_TOKEN)
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).path
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)
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@util.memoized_property
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def _loader_key(self):
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return ("loader", self.path)
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@property
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def mapper(self):
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return self.entity
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@property
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def entity_path(self):
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return self[self.entity]
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def __getitem__(self, entity):
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if isinstance(entity, (int, slice)):
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return self.path[entity]
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else:
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return EntityRegistry(
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self, entity
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)
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class EntityRegistry(PathRegistry, dict):
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is_aliased_class = False
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has_entity = True
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def __init__(self, parent, entity):
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self.key = entity
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self.parent = parent
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self.is_aliased_class = entity.is_aliased_class
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self.entity = entity
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self.path = parent.path + (entity,)
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self.entity_path = self
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@property
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def mapper(self):
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return inspection.inspect(self.entity).mapper
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def __bool__(self):
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return True
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__nonzero__ = __bool__
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def __getitem__(self, entity):
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if isinstance(entity, (int, slice)):
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return self.path[entity]
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else:
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return dict.__getitem__(self, entity)
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def __missing__(self, key):
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self[key] = item = PropRegistry(self, key)
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return item
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