# ext/associationproxy.py
# Copyright (C) 2005-2015 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
"""Contain the ``AssociationProxy`` class.
The ``AssociationProxy`` is a Python property object which provides
transparent proxied access to the endpoint of an association object.
See the example ``examples/association/proxied_association.py``.
"""
import itertools
import operator
import weakref
from .. import exc, orm, util
from ..orm import collections, interfaces
from ..sql import not_, or_
def association_proxy(target_collection, attr, **kw):
"""Return a Python property implementing a view of a target
attribute which references an attribute on members of the
target.
The returned value is an instance of :class:`.AssociationProxy`.
Implements a Python property representing a relationship as a collection
of simpler values, or a scalar value. The proxied property will mimic
the collection type of the target (list, dict or set), or, in the case of
a one to one relationship, a simple scalar value.
:param target_collection: Name of the attribute we'll proxy to.
This attribute is typically mapped by
:func:`~sqlalchemy.orm.relationship` to link to a target collection, but
can also be a many-to-one or non-scalar relationship.
:param attr: Attribute on the associated instance or instances we'll
proxy for.
For example, given a target collection of [obj1, obj2], a list created
by this proxy property would look like [getattr(obj1, *attr*),
getattr(obj2, *attr*)]
If the relationship is one-to-one or otherwise uselist=False, then
simply: getattr(obj, *attr*)
:param creator: optional.
When new items are added to this proxied collection, new instances of
the class collected by the target collection will be created. For list
and set collections, the target class constructor will be called with
the 'value' for the new instance. For dict types, two arguments are
passed: key and value.
If you want to construct instances differently, supply a *creator*
function that takes arguments as above and returns instances.
For scalar relationships, creator() will be called if the target is None.
If the target is present, set operations are proxied to setattr() on the
associated object.
If you have an associated object with multiple attributes, you may set
up multiple association proxies mapping to different attributes. See
the unit tests for examples, and for examples of how creator() functions
can be used to construct the scalar relationship on-demand in this
situation.
:param \*\*kw: Passes along any other keyword arguments to
:class:`.AssociationProxy`.
"""
return AssociationProxy(target_collection, attr, **kw)
ASSOCIATION_PROXY = util.symbol('ASSOCIATION_PROXY')
"""Symbol indicating an :class:`InspectionAttr` that's
of type :class:`.AssociationProxy`.
Is assigned to the :attr:`.InspectionAttr.extension_type`
attibute.
"""
class AssociationProxy(interfaces.InspectionAttrInfo):
"""A descriptor that presents a read/write view of an object attribute."""
is_attribute = False
extension_type = ASSOCIATION_PROXY
def __init__(self, target_collection, attr, creator=None,
getset_factory=None, proxy_factory=None,
proxy_bulk_set=None):
"""Construct a new :class:`.AssociationProxy`.
The :func:`.association_proxy` function is provided as the usual
entrypoint here, though :class:`.AssociationProxy` can be instantiated
and/or subclassed directly.
:param target_collection: Name of the collection we'll proxy to,
usually created with :func:`.relationship`.
:param attr: Attribute on the collected instances we'll proxy
for. For example, given a target collection of [obj1, obj2], a
list created by this proxy property would look like
[getattr(obj1, attr), getattr(obj2, attr)]
:param creator: Optional. When new items are added to this proxied
collection, new instances of the class collected by the target
collection will be created. For list and set collections, the
target class constructor will be called with the 'value' for the
new instance. For dict types, two arguments are passed:
key and value.
If you want to construct instances differently, supply a 'creator'
function that takes arguments as above and returns instances.
:param getset_factory: Optional. Proxied attribute access is
automatically handled by routines that get and set values based on
the `attr` argument for this proxy.
If you would like to customize this behavior, you may supply a
`getset_factory` callable that produces a tuple of `getter` and
`setter` functions. The factory is called with two arguments, the
abstract type of the underlying collection and this proxy instance.
:param proxy_factory: Optional. The type of collection to emulate is
determined by sniffing the target collection. If your collection
type can't be determined by duck typing or you'd like to use a
different collection implementation, you may supply a factory
function to produce those collections. Only applicable to
non-scalar relationships.
:param proxy_bulk_set: Optional, use with proxy_factory. See
the _set() method for details.
"""
self.target_collection = target_collection
self.value_attr = attr
self.creator = creator
self.getset_factory = getset_factory
self.proxy_factory = proxy_factory
self.proxy_bulk_set = proxy_bulk_set
self.owning_class = None
self.key = '_%s_%s_%s' % (
type(self).__name__, target_collection, id(self))
self.collection_class = None
@property
def remote_attr(self):
"""The 'remote' :class:`.MapperProperty` referenced by this
:class:`.AssociationProxy`.
.. versionadded:: 0.7.3
See also:
:attr:`.AssociationProxy.attr`
:attr:`.AssociationProxy.local_attr`
"""
return getattr(self.target_class, self.value_attr)
@property
def local_attr(self):
"""The 'local' :class:`.MapperProperty` referenced by this
:class:`.AssociationProxy`.
.. versionadded:: 0.7.3
See also:
:attr:`.AssociationProxy.attr`
:attr:`.AssociationProxy.remote_attr`
"""
return getattr(self.owning_class, self.target_collection)
@property
def attr(self):
"""Return a tuple of ``(local_attr, remote_attr)``.
This attribute is convenient when specifying a join
using :meth:`.Query.join` across two relationships::
sess.query(Parent).join(*Parent.proxied.attr)
.. versionadded:: 0.7.3
See also:
:attr:`.AssociationProxy.local_attr`
:attr:`.AssociationProxy.remote_attr`
"""
return (self.local_attr, self.remote_attr)
def _get_property(self):
return (orm.class_mapper(self.owning_class).
get_property(self.target_collection))
@util.memoized_property
def target_class(self):
"""The intermediary class handled by this :class:`.AssociationProxy`.
Intercepted append/set/assignment events will result
in the generation of new instances of this class.
"""
return self._get_property().mapper.class_
@util.memoized_property
def scalar(self):
"""Return ``True`` if this :class:`.AssociationProxy` proxies a scalar
relationship on the local side."""
scalar = not self._get_property().uselist
if scalar:
self._initialize_scalar_accessors()
return scalar
@util.memoized_property
def _value_is_scalar(self):
return not self._get_property().\
mapper.get_property(self.value_attr).uselist
@util.memoized_property
def _target_is_object(self):
return getattr(self.target_class, self.value_attr).impl.uses_objects
def __get__(self, obj, class_):
if self.owning_class is None:
self.owning_class = class_ and class_ or type(obj)
if obj is None:
return self
if self.scalar:
target = getattr(obj, self.target_collection)
return self._scalar_get(target)
else:
try:
# If the owning instance is reborn (orm session resurrect,
# etc.), refresh the proxy cache.
creator_id, proxy = getattr(obj, self.key)
if id(obj) == creator_id:
return proxy
except AttributeError:
pass
proxy = self._new(_lazy_collection(obj, self.target_collection))
setattr(obj, self.key, (id(obj), proxy))
return proxy
def __set__(self, obj, values):
if self.owning_class is None:
self.owning_class = type(obj)
if self.scalar:
creator = self.creator and self.creator or self.target_class
target = getattr(obj, self.target_collection)
if target is None:
setattr(obj, self.target_collection, creator(values))
else:
self._scalar_set(target, values)
else:
proxy = self.__get__(obj, None)
if proxy is not values:
proxy.clear()
self._set(proxy, values)
def __delete__(self, obj):
if self.owning_class is None:
self.owning_class = type(obj)
delattr(obj, self.key)
def _initialize_scalar_accessors(self):
if self.getset_factory:
get, set = self.getset_factory(None, self)
else:
get, set = self._default_getset(None)
self._scalar_get, self._scalar_set = get, set
def _default_getset(self, collection_class):
attr = self.value_attr
_getter = operator.attrgetter(attr)
getter = lambda target: _getter(target) if target is not None else None
if collection_class is dict:
setter = lambda o, k, v: setattr(o, attr, v)
else:
setter = lambda o, v: setattr(o, attr, v)
return getter, setter
def _new(self, lazy_collection):
creator = self.creator and self.creator or self.target_class
self.collection_class = util.duck_type_collection(lazy_collection())
if self.proxy_factory:
return self.proxy_factory(
lazy_collection, creator, self.value_attr, self)
if self.getset_factory:
getter, setter = self.getset_factory(self.collection_class, self)
else:
getter, setter = self._default_getset(self.collection_class)
if self.collection_class is list:
return _AssociationList(
lazy_collection, creator, getter, setter, self)
elif self.collection_class is dict:
return _AssociationDict(
lazy_collection, creator, getter, setter, self)
elif self.collection_class is set:
return _AssociationSet(
lazy_collection, creator, getter, setter, self)
else:
raise exc.ArgumentError(
'could not guess which interface to use for '
'collection_class "%s" backing "%s"; specify a '
'proxy_factory and proxy_bulk_set manually' %
(self.collection_class.__name__, self.target_collection))
def _inflate(self, proxy):
creator = self.creator and self.creator or self.target_class
if self.getset_factory:
getter, setter = self.getset_factory(self.collection_class, self)
else:
getter, setter = self._default_getset(self.collection_class)
proxy.creator = creator
proxy.getter = getter
proxy.setter = setter
def _set(self, proxy, values):
if self.proxy_bulk_set:
self.proxy_bulk_set(proxy, values)
elif self.collection_class is list:
proxy.extend(values)
elif self.collection_class is dict:
proxy.update(values)
elif self.collection_class is set:
proxy.update(values)
else:
raise exc.ArgumentError(
'no proxy_bulk_set supplied for custom '
'collection_class implementation')
@property
def _comparator(self):
return self._get_property().comparator
def any(self, criterion=None, **kwargs):
"""Produce a proxied 'any' expression using EXISTS.
This expression will be a composed product
using the :meth:`.RelationshipProperty.Comparator.any`
and/or :meth:`.RelationshipProperty.Comparator.has`
operators of the underlying proxied attributes.
"""
if self._target_is_object:
if self._value_is_scalar:
value_expr = getattr(
self.target_class, self.value_attr).has(
criterion, **kwargs)
else:
value_expr = getattr(
self.target_class, self.value_attr).any(
criterion, **kwargs)
else:
value_expr = criterion
# check _value_is_scalar here, otherwise
# we're scalar->scalar - call .any() so that
# the "can't call any() on a scalar" msg is raised.
if self.scalar and not self._value_is_scalar:
return self._comparator.has(
value_expr
)
else:
return self._comparator.any(
value_expr
)
def has(self, criterion=None, **kwargs):
"""Produce a proxied 'has' expression using EXISTS.
This expression will be a composed product
using the :meth:`.RelationshipProperty.Comparator.any`
and/or :meth:`.RelationshipProperty.Comparator.has`
operators of the underlying proxied attributes.
"""
if self._target_is_object:
return self._comparator.has(
getattr(self.target_class, self.value_attr).
has(criterion, **kwargs)
)
else:
if criterion is not None or kwargs:
raise exc.ArgumentError(
"Non-empty has() not allowed for "
"column-targeted association proxy; use ==")
return self._comparator.has()
def contains(self, obj):
"""Produce a proxied 'contains' expression using EXISTS.
This expression will be a composed product
using the :meth:`.RelationshipProperty.Comparator.any`
, :meth:`.RelationshipProperty.Comparator.has`,
and/or :meth:`.RelationshipProperty.Comparator.contains`
operators of the underlying proxied attributes.
"""
if self.scalar and not self._value_is_scalar:
return self._comparator.has(
getattr(self.target_class, self.value_attr).contains(obj)
)
else:
return self._comparator.any(**{self.value_attr: obj})
def __eq__(self, obj):
# note the has() here will fail for collections; eq_()
# is only allowed with a scalar.
if obj is None:
return or_(
self._comparator.has(**{self.value_attr: obj}),
self._comparator == None
)
else:
return self._comparator.has(**{self.value_attr: obj})
def __ne__(self, obj):
# note the has() here will fail for collections; eq_()
# is only allowed with a scalar.
return self._comparator.has(
getattr(self.target_class, self.value_attr) != obj)
class _lazy_collection(object):
def __init__(self, obj, target):
self.ref = weakref.ref(obj)
self.target = target
def __call__(self):
obj = self.ref()
if obj is None:
raise exc.InvalidRequestError(
"stale association proxy, parent object has gone out of "
"scope")
return getattr(obj, self.target)
def __getstate__(self):
return {'obj': self.ref(), 'target': self.target}
def __setstate__(self, state):
self.ref = weakref.ref(state['obj'])
self.target = state['target']
class _AssociationCollection(object):
def __init__(self, lazy_collection, creator, getter, setter, parent):
"""Constructs an _AssociationCollection.
This will always be a subclass of either _AssociationList,
_AssociationSet, or _AssociationDict.
lazy_collection
A callable returning a list-based collection of entities (usually an
object attribute managed by a SQLAlchemy relationship())
creator
A function that creates new target entities. Given one parameter:
value. This assertion is assumed::
obj = creator(somevalue)
assert getter(obj) == somevalue
getter
A function. Given an associated object, return the 'value'.
setter
A function. Given an associated object and a value, store that
value on the object.
"""
self.lazy_collection = lazy_collection
self.creator = creator
self.getter = getter
self.setter = setter
self.parent = parent
col = property(lambda self: self.lazy_collection())
def __len__(self):
return len(self.col)
def __bool__(self):
return bool(self.col)
__nonzero__ = __bool__
def __getstate__(self):
return {'parent': self.parent, 'lazy_collection': self.lazy_collection}
def __setstate__(self, state):
self.parent = state['parent']
self.lazy_collection = state['lazy_collection']
self.parent._inflate(self)
class _AssociationList(_AssociationCollection):
"""Generic, converting, list-to-list proxy."""
def _create(self, value):
return self.creator(value)
def _get(self, object):
return self.getter(object)
def _set(self, object, value):
return self.setter(object, value)
def __getitem__(self, index):
if not isinstance(index, slice):
return self._get(self.col[index])
else:
return [self._get(member) for member in self.col[index]]
def __setitem__(self, index, value):
if not isinstance(index, slice):
self._set(self.col[index], value)
else:
if index.stop is None:
stop = len(self)
elif index.stop < 0:
stop = len(self) + index.stop
else:
stop = index.stop
step = index.step or 1
start = index.start or 0
rng = list(range(index.start or 0, stop, step))
if step == 1:
for i in rng:
del self[start]
i = start
for item in value:
self.insert(i, item)
i += 1
else:
if len(value) != len(rng):
raise ValueError(
"attempt to assign sequence of size %s to "
"extended slice of size %s" % (len(value),
len(rng)))
for i, item in zip(rng, value):
self._set(self.col[i], item)
def __delitem__(self, index):
del self.col[index]
def __contains__(self, value):
for member in self.col:
# testlib.pragma exempt:__eq__
if self._get(member) == value:
return True
return False
def __getslice__(self, start, end):
return [self._get(member) for member in self.col[start:end]]
def __setslice__(self, start, end, values):
members = [self._create(v) for v in values]
self.col[start:end] = members
def __delslice__(self, start, end):
del self.col[start:end]
def __iter__(self):
"""Iterate over proxied values.
For the actual domain objects, iterate over .col instead or
just use the underlying collection directly from its property
on the parent.
"""
for member in self.col:
yield self._get(member)
raise StopIteration
def append(self, value):
item = self._create(value)
self.col.append(item)
def count(self, value):
return sum([1 for _ in
util.itertools_filter(lambda v: v == value, iter(self))])
def extend(self, values):
for v in values:
self.append(v)
def insert(self, index, value):
self.col[index:index] = [self._create(value)]
def pop(self, index=-1):
return self.getter(self.col.pop(index))
def remove(self, value):
for i, val in enumerate(self):
if val == value:
del self.col[i]
return
raise ValueError("value not in list")
def reverse(self):
"""Not supported, use reversed(mylist)"""
raise NotImplementedError
def sort(self):
"""Not supported, use sorted(mylist)"""
raise NotImplementedError
def clear(self):
del self.col[0:len(self.col)]
def __eq__(self, other):
return list(self) == other
def __ne__(self, other):
return list(self) != other
def __lt__(self, other):
return list(self) < other
def __le__(self, other):
return list(self) <= other
def __gt__(self, other):
return list(self) > other
def __ge__(self, other):
return list(self) >= other
def __cmp__(self, other):
return cmp(list(self), other)
def __add__(self, iterable):
try:
other = list(iterable)
except TypeError:
return NotImplemented
return list(self) + other
def __radd__(self, iterable):
try:
other = list(iterable)
except TypeError:
return NotImplemented
return other + list(self)
def __mul__(self, n):
if not isinstance(n, int):
return NotImplemented
return list(self) * n
__rmul__ = __mul__
def __iadd__(self, iterable):
self.extend(iterable)
return self
def __imul__(self, n):
# unlike a regular list *=, proxied __imul__ will generate unique
# backing objects for each copy. *= on proxied lists is a bit of
# a stretch anyhow, and this interpretation of the __imul__ contract
# is more plausibly useful than copying the backing objects.
if not isinstance(n, int):
return NotImplemented
if n == 0:
self.clear()
elif n > 1:
self.extend(list(self) * (n - 1))
return self
def copy(self):
return list(self)
def __repr__(self):
return repr(list(self))
def __hash__(self):
raise TypeError("%s objects are unhashable" % type(self).__name__)
for func_name, func in list(locals().items()):
if (util.callable(func) and func.__name__ == func_name and
not func.__doc__ and hasattr(list, func_name)):
func.__doc__ = getattr(list, func_name).__doc__
del func_name, func
_NotProvided = util.symbol('_NotProvided')
class _AssociationDict(_AssociationCollection):
"""Generic, converting, dict-to-dict proxy."""
def _create(self, key, value):
return self.creator(key, value)
def _get(self, object):
return self.getter(object)
def _set(self, object, key, value):
return self.setter(object, key, value)
def __getitem__(self, key):
return self._get(self.col[key])
def __setitem__(self, key, value):
if key in self.col:
self._set(self.col[key], key, value)
else:
self.col[key] = self._create(key, value)
def __delitem__(self, key):
del self.col[key]
def __contains__(self, key):
# testlib.pragma exempt:__hash__
return key in self.col
def has_key(self, key):
# testlib.pragma exempt:__hash__
return key in self.col
def __iter__(self):
return iter(self.col.keys())
def clear(self):
self.col.clear()
def __eq__(self, other):
return dict(self) == other
def __ne__(self, other):
return dict(self) != other
def __lt__(self, other):
return dict(self) < other
def __le__(self, other):
return dict(self) <= other
def __gt__(self, other):
return dict(self) > other
def __ge__(self, other):
return dict(self) >= other
def __cmp__(self, other):
return cmp(dict(self), other)
def __repr__(self):
return repr(dict(self.items()))
def get(self, key, default=None):
try:
return self[key]
except KeyError:
return default
def setdefault(self, key, default=None):
if key not in self.col:
self.col[key] = self._create(key, default)
return default
else:
return self[key]
def keys(self):
return self.col.keys()
if util.py2k:
def iteritems(self):
return ((key, self._get(self.col[key])) for key in self.col)
def itervalues(self):
return (self._get(self.col[key]) for key in self.col)
def iterkeys(self):
return self.col.iterkeys()
def values(self):
return [self._get(member) for member in self.col.values()]
def items(self):
return [(k, self._get(self.col[k])) for k in self]
else:
def items(self):
return ((key, self._get(self.col[key])) for key in self.col)
def values(self):
return (self._get(self.col[key]) for key in self.col)
def pop(self, key, default=_NotProvided):
if default is _NotProvided:
member = self.col.pop(key)
else:
member = self.col.pop(key, default)
return self._get(member)
def popitem(self):
item = self.col.popitem()
return (item[0], self._get(item[1]))
def update(self, *a, **kw):
if len(a) > 1:
raise TypeError('update expected at most 1 arguments, got %i' %
len(a))
elif len(a) == 1:
seq_or_map = a[0]
# discern dict from sequence - took the advice from
# http://www.voidspace.org.uk/python/articles/duck_typing.shtml
# still not perfect :(
if hasattr(seq_or_map, 'keys'):
for item in seq_or_map:
self[item] = seq_or_map[item]
else:
try:
for k, v in seq_or_map:
self[k] = v
except ValueError:
raise ValueError(
"dictionary update sequence "
"requires 2-element tuples")
for key, value in kw:
self[key] = value
def copy(self):
return dict(self.items())
def __hash__(self):
raise TypeError("%s objects are unhashable" % type(self).__name__)
for func_name, func in list(locals().items()):
if (util.callable(func) and func.__name__ == func_name and
not func.__doc__ and hasattr(dict, func_name)):
func.__doc__ = getattr(dict, func_name).__doc__
del func_name, func
class _AssociationSet(_AssociationCollection):
"""Generic, converting, set-to-set proxy."""
def _create(self, value):
return self.creator(value)
def _get(self, object):
return self.getter(object)
def _set(self, object, value):
return self.setter(object, value)
def __len__(self):
return len(self.col)
def __bool__(self):
if self.col:
return True
else:
return False
__nonzero__ = __bool__
def __contains__(self, value):
for member in self.col:
# testlib.pragma exempt:__eq__
if self._get(member) == value:
return True
return False
def __iter__(self):
"""Iterate over proxied values.
For the actual domain objects, iterate over .col instead or just use
the underlying collection directly from its property on the parent.
"""
for member in self.col:
yield self._get(member)
raise StopIteration
def add(self, value):
if value not in self:
self.col.add(self._create(value))
# for discard and remove, choosing a more expensive check strategy rather
# than call self.creator()
def discard(self, value):
for member in self.col:
if self._get(member) == value:
self.col.discard(member)
break
def remove(self, value):
for member in self.col:
if self._get(member) == value:
self.col.discard(member)
return
raise KeyError(value)
def pop(self):
if not self.col:
raise KeyError('pop from an empty set')
member = self.col.pop()
return self._get(member)
def update(self, other):
for value in other:
self.add(value)
def __ior__(self, other):
if not collections._set_binops_check_strict(self, other):
return NotImplemented
for value in other:
self.add(value)
return self
def _set(self):
return set(iter(self))
def union(self, other):
return set(self).union(other)
__or__ = union
def difference(self, other):
return set(self).difference(other)
__sub__ = difference
def difference_update(self, other):
for value in other:
self.discard(value)
def __isub__(self, other):
if not collections._set_binops_check_strict(self, other):
return NotImplemented
for value in other:
self.discard(value)
return self
def intersection(self, other):
return set(self).intersection(other)
__and__ = intersection
def intersection_update(self, other):
want, have = self.intersection(other), set(self)
remove, add = have - want, want - have
for value in remove:
self.remove(value)
for value in add:
self.add(value)
def __iand__(self, other):
if not collections._set_binops_check_strict(self, other):
return NotImplemented
want, have = self.intersection(other), set(self)
remove, add = have - want, want - have
for value in remove:
self.remove(value)
for value in add:
self.add(value)
return self
def symmetric_difference(self, other):
return set(self).symmetric_difference(other)
__xor__ = symmetric_difference
def symmetric_difference_update(self, other):
want, have = self.symmetric_difference(other), set(self)
remove, add = have - want, want - have
for value in remove:
self.remove(value)
for value in add:
self.add(value)
def __ixor__(self, other):
if not collections._set_binops_check_strict(self, other):
return NotImplemented
want, have = self.symmetric_difference(other), set(self)
remove, add = have - want, want - have
for value in remove:
self.remove(value)
for value in add:
self.add(value)
return self
def issubset(self, other):
return set(self).issubset(other)
def issuperset(self, other):
return set(self).issuperset(other)
def clear(self):
self.col.clear()
def copy(self):
return set(self)
def __eq__(self, other):
return set(self) == other
def __ne__(self, other):
return set(self) != other
def __lt__(self, other):
return set(self) < other
def __le__(self, other):
return set(self) <= other
def __gt__(self, other):
return set(self) > other
def __ge__(self, other):
return set(self) >= other
def __repr__(self):
return repr(set(self))
def __hash__(self):
raise TypeError("%s objects are unhashable" % type(self).__name__)
for func_name, func in list(locals().items()):
if (util.callable(func) and func.__name__ == func_name and
not func.__doc__ and hasattr(set, func_name)):
func.__doc__ = getattr(set, func_name).__doc__
del func_name, func