# ext/declarative/base.py
# Copyright (C) 2005-2020 the SQLAlchemy authors and contributors
# <see AUTHORS file>
#
# This module is part of SQLAlchemy and is released under
# the MIT License: http://www.opensource.org/licenses/mit-license.php
"""Internal implementation for declarative."""
from __future__ import absolute_import
import collections
import weakref
from sqlalchemy.orm import attributes
from sqlalchemy.orm import instrumentation
from . import clsregistry
from . import exc as orm_exc
from . import mapper as mapperlib
from .attributes import QueryableAttribute
from .base import _is_mapped_class
from .base import InspectionAttr
from .descriptor_props import CompositeProperty
from .descriptor_props import SynonymProperty
from .interfaces import MapperProperty
from .mapper import Mapper as mapper
from .properties import ColumnProperty
from .util import class_mapper
from .. import event
from .. import exc
from .. import util
from ..sql import expression
from ..sql.schema import Column
from ..sql.schema import Table
from ..util import topological
def _declared_mapping_info(cls):
# deferred mapping
if _DeferredMapperConfig.has_cls(cls):
return _DeferredMapperConfig.config_for_cls(cls)
# regular mapping
elif _is_mapped_class(cls):
return class_mapper(cls, configure=False)
else:
return None
def _resolve_for_abstract_or_classical(cls):
if cls is object:
return None
if cls.__dict__.get("__abstract__", False):
for sup in cls.__bases__:
sup = _resolve_for_abstract_or_classical(sup)
if sup is not None:
return sup
else:
return None
else:
clsmanager = _dive_for_cls_manager(cls)
if clsmanager:
return clsmanager.class_
else:
return cls
def _get_immediate_cls_attr(cls, attrname, strict=False):
"""return an attribute of the class that is either present directly
on the class, e.g. not on a superclass, or is from a superclass but
this superclass is a non-mapped mixin, that is, not a descendant of
the declarative base and is also not classically mapped.
This is used to detect attributes that indicate something about
a mapped class independently from any mapped classes that it may
inherit from.
"""
# the rules are different for this name than others,
# make sure we've moved it out. transitional
assert attrname != "__abstract__"
if not issubclass(cls, object):
return None
if attrname in cls.__dict__:
return getattr(cls, attrname)
for base in cls.__mro__[1:]:
_is_classicial_inherits = _dive_for_cls_manager(base)
if attrname in base.__dict__ and (
base is cls
or (
(base in cls.__bases__ if strict else True)
and not _is_classicial_inherits
)
):
return getattr(base, attrname)
else:
return None
def _dive_for_cls_manager(cls):
# because the class manager registration is pluggable,
# we need to do the search for every class in the hierarchy,
# rather than just a simple "cls._sa_class_manager"
# python 2 old style class
if not hasattr(cls, "__mro__"):
return None
for base in cls.__mro__:
manager = attributes.manager_of_class(base)
if manager:
return manager
return None
def _as_declarative(registry, cls, dict_):
# declarative scans the class for attributes. no table or mapper
# args passed separately.
return _MapperConfig.setup_mapping(registry, cls, dict_, None, {})
def _mapper(registry, cls, table, mapper_kw):
_ImperativeMapperConfig(registry, cls, table, mapper_kw)
return cls.__mapper__
@util.preload_module("sqlalchemy.orm.decl_api")
def _is_declarative_props(obj):
declared_attr = util.preloaded.orm_decl_api.declared_attr
return isinstance(obj, (declared_attr, util.classproperty))
def _check_declared_props_nocascade(obj, name, cls):
if _is_declarative_props(obj):
if getattr(obj, "_cascading", False):
util.warn(
"@declared_attr.cascading is not supported on the %s "
"attribute on class %s. This attribute invokes for "
"subclasses in any case." % (name, cls)
)
return True
else:
return False
class _MapperConfig(object):
__slots__ = ("cls", "classname", "properties", "declared_attr_reg")
@classmethod
def setup_mapping(cls, registry, cls_, dict_, table, mapper_kw):
manager = attributes.manager_of_class(cls)
if manager and manager.class_ is cls_:
raise exc.InvalidRequestError(
"Class %r already has been " "instrumented declaratively" % cls
)
if cls_.__dict__.get("__abstract__", False):
return
defer_map = _get_immediate_cls_attr(
cls_, "_sa_decl_prepare_nocascade", strict=True
) or hasattr(cls_, "_sa_decl_prepare")
if defer_map:
cfg_cls = _DeferredMapperConfig
else:
cfg_cls = _ClassScanMapperConfig
return cfg_cls(registry, cls_, dict_, table, mapper_kw)
def __init__(self, registry, cls_):
self.cls = cls_
self.classname = cls_.__name__
self.properties = util.OrderedDict()
self.declared_attr_reg = {}
instrumentation.register_class(
self.cls,
finalize=False,
registry=registry,
declarative_scan=self,
init_method=registry.constructor,
)
def set_cls_attribute(self, attrname, value):
manager = instrumentation.manager_of_class(self.cls)
manager.install_member(attrname, value)
return value
def _early_mapping(self, mapper_kw):
self.map(mapper_kw)
class _ImperativeMapperConfig(_MapperConfig):
__slots__ = ("dict_", "local_table", "inherits")
def __init__(
self,
registry,
cls_,
table,
mapper_kw,
):
super(_ImperativeMapperConfig, self).__init__(registry, cls_)
self.dict_ = {}
self.local_table = self.set_cls_attribute("__table__", table)
with mapperlib._CONFIGURE_MUTEX:
clsregistry.add_class(
self.classname, self.cls, registry._class_registry
)
self._setup_inheritance(mapper_kw)
self._early_mapping(mapper_kw)
def map(self, mapper_kw=util.EMPTY_DICT):
mapper_cls = mapper
return self.set_cls_attribute(
"__mapper__",
mapper_cls(self.cls, self.local_table, **mapper_kw),
)
def _setup_inheritance(self, mapper_kw):
cls = self.cls
inherits = mapper_kw.get("inherits", None)
if inherits is None:
# since we search for classical mappings now, search for
# multiple mapped bases as well and raise an error.
inherits_search = []
for c in cls.__bases__:
c = _resolve_for_abstract_or_classical(c)
if c is None:
continue
if _declared_mapping_info(
c
) is not None and not _get_immediate_cls_attr(
c, "_sa_decl_prepare_nocascade", strict=True
):
inherits_search.append(c)
if inherits_search:
if len(inherits_search) > 1:
raise exc.InvalidRequestError(
"Class %s has multiple mapped bases: %r"
% (cls, inherits_search)
)
inherits = inherits_search[0]
elif isinstance(inherits, mapper):
inherits = inherits.class_
self.inherits = inherits
class _ClassScanMapperConfig(_MapperConfig):
__slots__ = (
"dict_",
"local_table",
"persist_selectable",
"declared_columns",
"column_copies",
"table_args",
"tablename",
"mapper_args",
"mapper_args_fn",
"inherits",
)
def __init__(
self,
registry,
cls_,
dict_,
table,
mapper_kw,
):
super(_ClassScanMapperConfig, self).__init__(registry, cls_)
self.dict_ = dict(dict_) if dict_ else {}
self.persist_selectable = None
self.declared_columns = set()
self.column_copies = {}
self._setup_declared_events()
self._scan_attributes()
with mapperlib._CONFIGURE_MUTEX:
clsregistry.add_class(
self.classname, self.cls, registry._class_registry
)
self._extract_mappable_attributes()
self._extract_declared_columns()
self._setup_table(table)
self._setup_inheritance(mapper_kw)
self._early_mapping(mapper_kw)
def _setup_declared_events(self):
if _get_immediate_cls_attr(self.cls, "__declare_last__"):
@event.listens_for(mapper, "after_configured")
def after_configured():
self.cls.__declare_last__()
if _get_immediate_cls_attr(self.cls, "__declare_first__"):
@event.listens_for(mapper, "before_configured")
def before_configured():
self.cls.__declare_first__()
def _scan_attributes(self):
cls = self.cls
dict_ = self.dict_
column_copies = self.column_copies
mapper_args_fn = None
table_args = inherited_table_args = None
tablename = None
for base in cls.__mro__:
class_mapped = (
base is not cls
and _declared_mapping_info(base) is not None
and not _get_immediate_cls_attr(
base, "_sa_decl_prepare_nocascade", strict=True
)
)
if not class_mapped and base is not cls:
self._produce_column_copies(base)
for name, obj in vars(base).items():
if name == "__mapper_args__":
check_decl = _check_declared_props_nocascade(
obj, name, cls
)
if not mapper_args_fn and (not class_mapped or check_decl):
# don't even invoke __mapper_args__ until
# after we've determined everything about the
# mapped table.
# make a copy of it so a class-level dictionary
# is not overwritten when we update column-based
# arguments.
def mapper_args_fn():
return dict(cls.__mapper_args__)
elif name == "__tablename__":
check_decl = _check_declared_props_nocascade(
obj, name, cls
)
if not tablename and (not class_mapped or check_decl):
tablename = cls.__tablename__
elif name == "__table_args__":
check_decl = _check_declared_props_nocascade(
obj, name, cls
)
if not table_args and (not class_mapped or check_decl):
table_args = cls.__table_args__
if not isinstance(
table_args, (tuple, dict, type(None))
):
raise exc.ArgumentError(
"__table_args__ value must be a tuple, "
"dict, or None"
)
if base is not cls:
inherited_table_args = True
elif class_mapped:
if _is_declarative_props(obj):
util.warn(
"Regular (i.e. not __special__) "
"attribute '%s.%s' uses @declared_attr, "
"but owning class %s is mapped - "
"not applying to subclass %s."
% (base.__name__, name, base, cls)
)
continue
elif base is not cls:
# we're a mixin, abstract base, or something that is
# acting like that for now.
if isinstance(obj, Column):
# already copied columns to the mapped class.
continue
elif isinstance(obj, MapperProperty):
raise exc.InvalidRequestError(
"Mapper properties (i.e. deferred,"
"column_property(), relationship(), etc.) must "
"be declared as @declared_attr callables "
"on declarative mixin classes."
)
elif _is_declarative_props(obj):
if obj._cascading:
if name in dict_:
# unfortunately, while we can use the user-
# defined attribute here to allow a clean
# override, if there's another
# subclass below then it still tries to use
# this. not sure if there is enough
# information here to add this as a feature
# later on.
util.warn(
"Attribute '%s' on class %s cannot be "
"processed due to "
"@declared_attr.cascading; "
"skipping" % (name, cls)
)
dict_[name] = column_copies[
obj
] = ret = obj.__get__(obj, cls)
setattr(cls, name, ret)
else:
# access attribute using normal class access
ret = getattr(cls, name)
# correct for proxies created from hybrid_property
# or similar. note there is no known case that
# produces nested proxies, so we are only
# looking one level deep right now.
if (
isinstance(ret, InspectionAttr)
and ret._is_internal_proxy
and not isinstance(
ret.original_property, MapperProperty
)
):
ret = ret.descriptor
dict_[name] = column_copies[obj] = ret
if (
isinstance(ret, (Column, MapperProperty))
and ret.doc is None
):
ret.doc = obj.__doc__
# here, the attribute is some other kind of property that
# we assume is not part of the declarative mapping.
# however, check for some more common mistakes
else:
self._warn_for_decl_attributes(base, name, obj)
if inherited_table_args and not tablename:
table_args = None
self.table_args = table_args
self.tablename = tablename
self.mapper_args_fn = mapper_args_fn
def _warn_for_decl_attributes(self, cls, key, c):
if isinstance(c, expression.ColumnClause):
util.warn(
"Attribute '%s' on class %s appears to be a non-schema "
"'sqlalchemy.sql.column()' "
"object; this won't be part of the declarative mapping"
% (key, cls)
)
def _produce_column_copies(self, base):
cls = self.cls
dict_ = self.dict_
column_copies = self.column_copies
# copy mixin columns to the mapped class
for name, obj in vars(base).items():
if isinstance(obj, Column):
if getattr(cls, name) is not obj:
# if column has been overridden
# (like by the InstrumentedAttribute of the
# superclass), skip
continue
elif obj.foreign_keys:
raise exc.InvalidRequestError(
"Columns with foreign keys to other columns "
"must be declared as @declared_attr callables "
"on declarative mixin classes. "
)
elif name not in dict_ and not (
"__table__" in dict_
and (obj.name or name) in dict_["__table__"].c
):
column_copies[obj] = copy_ = obj.copy()
copy_._creation_order = obj._creation_order
setattr(cls, name, copy_)
dict_[name] = copy_
def _extract_mappable_attributes(self):
cls = self.cls
dict_ = self.dict_
our_stuff = self.properties
late_mapped = _get_immediate_cls_attr(
cls, "_sa_decl_prepare_nocascade", strict=True
)
for k in list(dict_):
if k in ("__table__", "__tablename__", "__mapper_args__"):
continue
value = dict_[k]
if _is_declarative_props(value):
if value._cascading:
util.warn(
"Use of @declared_attr.cascading only applies to "
"Declarative 'mixin' and 'abstract' classes. "
"Currently, this flag is ignored on mapped class "
"%s" % self.cls
)
value = getattr(cls, k)
elif (
isinstance(value, QueryableAttribute)
and value.class_ is not cls
and value.key != k
):
# detect a QueryableAttribute that's already mapped being
# assigned elsewhere in userland, turn into a synonym()
value = SynonymProperty(value.key)
setattr(cls, k, value)
if (
isinstance(value, tuple)
and len(value) == 1
and isinstance(value[0], (Column, MapperProperty))
):
util.warn(
"Ignoring declarative-like tuple value of attribute "
"'%s': possibly a copy-and-paste error with a comma "
"accidentally placed at the end of the line?" % k
)
continue
elif not isinstance(value, (Column, MapperProperty)):
# using @declared_attr for some object that
# isn't Column/MapperProperty; remove from the dict_
# and place the evaluated value onto the class.
if not k.startswith("__"):
dict_.pop(k)
self._warn_for_decl_attributes(cls, k, value)
if not late_mapped:
setattr(cls, k, value)
continue
# we expect to see the name 'metadata' in some valid cases;
# however at this point we see it's assigned to something trying
# to be mapped, so raise for that.
elif k == "metadata":
raise exc.InvalidRequestError(
"Attribute name 'metadata' is reserved "
"for the MetaData instance when using a "
"declarative base class."
)
our_stuff[k] = value
def _extract_declared_columns(self):
our_stuff = self.properties
# set up attributes in the order they were created
our_stuff.sort(key=lambda key: our_stuff[key]._creation_order)
# extract columns from the class dict
declared_columns = self.declared_columns
name_to_prop_key = collections.defaultdict(set)
for key, c in list(our_stuff.items()):
if isinstance(c, (ColumnProperty, CompositeProperty)):
for col in c.columns:
if isinstance(col, Column) and col.table is None:
_undefer_column_name(key, col)
if not isinstance(c, CompositeProperty):
name_to_prop_key[col.name].add(key)
declared_columns.add(col)
elif isinstance(c, Column):
_undefer_column_name(key, c)
name_to_prop_key[c.name].add(key)
declared_columns.add(c)
# if the column is the same name as the key,
# remove it from the explicit properties dict.
# the normal rules for assigning column-based properties
# will take over, including precedence of columns
# in multi-column ColumnProperties.
if key == c.key:
del our_stuff[key]
for name, keys in name_to_prop_key.items():
if len(keys) > 1:
util.warn(
"On class %r, Column object %r named "
"directly multiple times, "
"only one will be used: %s. "
"Consider using orm.synonym instead"
% (self.classname, name, (", ".join(sorted(keys))))
)
def _setup_table(self, table=None):
cls = self.cls
tablename = self.tablename
table_args = self.table_args
dict_ = self.dict_
declared_columns = self.declared_columns
manager = attributes.manager_of_class(cls)
declared_columns = self.declared_columns = sorted(
declared_columns, key=lambda c: c._creation_order
)
if "__table__" not in dict_ and table is None:
if hasattr(cls, "__table_cls__"):
table_cls = util.unbound_method_to_callable(cls.__table_cls__)
else:
table_cls = Table
if tablename is not None:
args, table_kw = (), {}
if table_args:
if isinstance(table_args, dict):
table_kw = table_args
elif isinstance(table_args, tuple):
if isinstance(table_args[-1], dict):
args, table_kw = table_args[0:-1], table_args[-1]
else:
args = table_args
autoload = dict_.get("__autoload__")
if autoload:
table_kw["autoload"] = True
table = self.set_cls_attribute(
"__table__",
table_cls(
tablename,
manager.registry.metadata,
*(tuple(declared_columns) + tuple(args)),
**table_kw
),
)
else:
if table is None:
table = cls.__table__
if declared_columns:
for c in declared_columns:
if not table.c.contains_column(c):
raise exc.ArgumentError(
"Can't add additional column %r when "
"specifying __table__" % c.key
)
self.local_table = table
def _setup_inheritance(self, mapper_kw):
table = self.local_table
cls = self.cls
table_args = self.table_args
declared_columns = self.declared_columns
inherits = mapper_kw.get("inherits", None)
if inherits is None:
# since we search for classical mappings now, search for
# multiple mapped bases as well and raise an error.
inherits_search = []
for c in cls.__bases__:
c = _resolve_for_abstract_or_classical(c)
if c is None:
continue
if _declared_mapping_info(
c
) is not None and not _get_immediate_cls_attr(
c, "_sa_decl_prepare_nocascade", strict=True
):
if c not in inherits_search:
inherits_search.append(c)
if inherits_search:
if len(inherits_search) > 1:
raise exc.InvalidRequestError(
"Class %s has multiple mapped bases: %r"
% (cls, inherits_search)
)
inherits = inherits_search[0]
elif isinstance(inherits, mapper):
inherits = inherits.class_
self.inherits = inherits
if (
table is None
and self.inherits is None
and not _get_immediate_cls_attr(cls, "__no_table__")
):
raise exc.InvalidRequestError(
"Class %r does not have a __table__ or __tablename__ "
"specified and does not inherit from an existing "
"table-mapped class." % cls
)
elif self.inherits:
inherited_mapper = _declared_mapping_info(self.inherits)
inherited_table = inherited_mapper.local_table
inherited_persist_selectable = inherited_mapper.persist_selectable
if table is None:
# single table inheritance.
# ensure no table args
if table_args:
raise exc.ArgumentError(
"Can't place __table_args__ on an inherited class "
"with no table."
)
# add any columns declared here to the inherited table.
for c in declared_columns:
if c.name in inherited_table.c:
if inherited_table.c[c.name] is c:
continue
raise exc.ArgumentError(
"Column '%s' on class %s conflicts with "
"existing column '%s'"
% (c, cls, inherited_table.c[c.name])
)
if c.primary_key:
raise exc.ArgumentError(
"Can't place primary key columns on an inherited "
"class with no table."
)
inherited_table.append_column(c)
if (
inherited_persist_selectable is not None
and inherited_persist_selectable is not inherited_table
):
inherited_persist_selectable._refresh_for_new_column(c)
def _prepare_mapper_arguments(self, mapper_kw):
properties = self.properties
if self.mapper_args_fn:
mapper_args = self.mapper_args_fn()
else:
mapper_args = {}
if mapper_kw:
mapper_args.update(mapper_kw)
if "properties" in mapper_args:
properties = dict(properties)
properties.update(mapper_args["properties"])
# make sure that column copies are used rather
# than the original columns from any mixins
for k in ("version_id_col", "polymorphic_on"):
if k in mapper_args:
v = mapper_args[k]
mapper_args[k] = self.column_copies.get(v, v)
if "inherits" in mapper_args:
inherits_arg = mapper_args["inherits"]
if isinstance(inherits_arg, mapper):
inherits_arg = inherits_arg.class_
if inherits_arg is not self.inherits:
raise exc.InvalidRequestError(
"mapper inherits argument given for non-inheriting "
"class %s" % (mapper_args["inherits"])
)
if self.inherits:
mapper_args["inherits"] = self.inherits
if self.inherits and not mapper_args.get("concrete", False):
# single or joined inheritance
# exclude any cols on the inherited table which are
# not mapped on the parent class, to avoid
# mapping columns specific to sibling/nephew classes
inherited_mapper = _declared_mapping_info(self.inherits)
inherited_table = inherited_mapper.local_table
if "exclude_properties" not in mapper_args:
mapper_args["exclude_properties"] = exclude_properties = set(
[
c.key
for c in inherited_table.c
if c not in inherited_mapper._columntoproperty
]
).union(inherited_mapper.exclude_properties or ())
exclude_properties.difference_update(
[c.key for c in self.declared_columns]
)
# look through columns in the current mapper that
# are keyed to a propname different than the colname
# (if names were the same, we'd have popped it out above,
# in which case the mapper makes this combination).
# See if the superclass has a similar column property.
# If so, join them together.
for k, col in list(properties.items()):
if not isinstance(col, expression.ColumnElement):
continue
if k in inherited_mapper._props:
p = inherited_mapper._props[k]
if isinstance(p, ColumnProperty):
# note here we place the subclass column
# first. See [ticket:1892] for background.
properties[k] = [col] + p.columns
result_mapper_args = mapper_args.copy()
result_mapper_args["properties"] = properties
self.mapper_args = result_mapper_args
def map(self, mapper_kw=util.EMPTY_DICT):
self._prepare_mapper_arguments(mapper_kw)
if hasattr(self.cls, "__mapper_cls__"):
mapper_cls = util.unbound_method_to_callable(
self.cls.__mapper_cls__
)
else:
mapper_cls = mapper
return self.set_cls_attribute(
"__mapper__",
mapper_cls(self.cls, self.local_table, **self.mapper_args),
)
class _DeferredMapperConfig(_ClassScanMapperConfig):
_configs = util.OrderedDict()
def _early_mapping(self, mapper_kw):
pass
@property
def cls(self):
return self._cls()
@cls.setter
def cls(self, class_):
self._cls = weakref.ref(class_, self._remove_config_cls)
self._configs[self._cls] = self
@classmethod
def _remove_config_cls(cls, ref):
cls._configs.pop(ref, None)
@classmethod
def has_cls(cls, class_):
# 2.6 fails on weakref if class_ is an old style class
return isinstance(class_, type) and weakref.ref(class_) in cls._configs
@classmethod
def raise_unmapped_for_cls(cls, class_):
if hasattr(class_, "_sa_raise_deferred_config"):
class_._sa_raise_deferred_config()
raise orm_exc.UnmappedClassError(
class_,
msg="Class %s has a deferred mapping on it. It is not yet "
"usable as a mapped class." % orm_exc._safe_cls_name(class_),
)
@classmethod
def config_for_cls(cls, class_):
return cls._configs[weakref.ref(class_)]
@classmethod
def classes_for_base(cls, base_cls, sort=True):
classes_for_base = [
m
for m, cls_ in [(m, m.cls) for m in cls._configs.values()]
if cls_ is not None and issubclass(cls_, base_cls)
]
if not sort:
return classes_for_base
all_m_by_cls = dict((m.cls, m) for m in classes_for_base)
tuples = []
for m_cls in all_m_by_cls:
tuples.extend(
(all_m_by_cls[base_cls], all_m_by_cls[m_cls])
for base_cls in m_cls.__bases__
if base_cls in all_m_by_cls
)
return list(topological.sort(tuples, classes_for_base))
def map(self, mapper_kw=util.EMPTY_DICT):
self._configs.pop(self._cls, None)
return super(_DeferredMapperConfig, self).map(mapper_kw)
def _add_attribute(cls, key, value):
"""add an attribute to an existing declarative class.
This runs through the logic to determine MapperProperty,
adds it to the Mapper, adds a column to the mapped Table, etc.
"""
if "__mapper__" in cls.__dict__:
if isinstance(value, Column):
_undefer_column_name(key, value)
cls.__table__.append_column(value, replace_existing=True)
cls.__mapper__.add_property(key, value)
elif isinstance(value, ColumnProperty):
for col in value.columns:
if isinstance(col, Column) and col.table is None:
_undefer_column_name(key, col)
cls.__table__.append_column(col, replace_existing=True)
cls.__mapper__.add_property(key, value)
elif isinstance(value, MapperProperty):
cls.__mapper__.add_property(key, value)
elif isinstance(value, QueryableAttribute) and value.key != key:
# detect a QueryableAttribute that's already mapped being
# assigned elsewhere in userland, turn into a synonym()
value = SynonymProperty(value.key)
cls.__mapper__.add_property(key, value)
else:
type.__setattr__(cls, key, value)
cls.__mapper__._expire_memoizations()
else:
type.__setattr__(cls, key, value)
def _del_attribute(cls, key):
if (
"__mapper__" in cls.__dict__
and key in cls.__dict__
and not cls.__mapper__._dispose_called
):
value = cls.__dict__[key]
if isinstance(
value, (Column, ColumnProperty, MapperProperty, QueryableAttribute)
):
raise NotImplementedError(
"Can't un-map individual mapped attributes on a mapped class."
)
else:
type.__delattr__(cls, key)
cls.__mapper__._expire_memoizations()
else:
type.__delattr__(cls, key)
def _declarative_constructor(self, **kwargs):
"""A simple constructor that allows initialization from kwargs.
Sets attributes on the constructed instance using the names and
values in ``kwargs``.
Only keys that are present as
attributes of the instance's class are allowed. These could be,
for example, any mapped columns or relationships.
"""
cls_ = type(self)
for k in kwargs:
if not hasattr(cls_, k):
raise TypeError(
"%r is an invalid keyword argument for %s" % (k, cls_.__name__)
)
setattr(self, k, kwargs[k])
_declarative_constructor.__name__ = "__init__"
def _undefer_column_name(key, column):
if column.key is None:
column.key = key
if column.name is None:
column.name = key