Viewing file:  Memory.py (5.79 KB) -rw-r--r--
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from __future__ import generators
ANY = None
from rdflib.store import Store
class Memory(Store):
"""\
An in memory implementation of a triple store.
This triple store uses nested dictionaries to store triples. Each
triple is stored in two such indices as follows spo[s][p][o] = 1 and
pos[p][o][s] = 1.
"""
def __init__(self, configuration=None, identifier=None):
super(Memory, self).__init__(configuration)
self.identifier = identifier
# indexed by [subject][predicate][object]
self.__spo = {}
# indexed by [predicate][object][subject]
self.__pos = {}
# indexed by [predicate][object][subject]
self.__osp = {}
self.__namespace = {}
self.__prefix = {}
def add(self, (subject, predicate, object), context, quoted=False):
"""\
Add a triple to the store of triples.
"""
# add dictionary entries for spo[s][p][p] = 1 and pos[p][o][s]
# = 1, creating the nested dictionaries where they do not yet
# exits.
spo = self.__spo
try:
po = spo[subject]
except:
po = spo[subject] = {}
try:
o = po[predicate]
except:
o = po[predicate] = {}
o[object] = 1
pos = self.__pos
try:
os = pos[predicate]
except:
os = pos[predicate] = {}
try:
s = os[object]
except:
s = os[object] = {}
s[subject] = 1
osp = self.__osp
try:
sp = osp[object]
except:
sp = osp[object] = {}
try:
p = sp[subject]
except:
p = sp[subject] = {}
p[predicate] = 1
def remove(self, (subject, predicate, object), context=None):
for (subject, predicate, object), c in self.triples((subject, predicate, object)):
del self.__spo[subject][predicate][object]
del self.__pos[predicate][object][subject]
del self.__osp[object][subject][predicate]
def triples(self, (subject, predicate, object), context=None):
"""A generator over all the triples matching """
if subject!=ANY: # subject is given
spo = self.__spo
if subject in spo:
subjectDictionary = spo[subject]
if predicate!=ANY: # subject+predicate is given
if predicate in subjectDictionary:
if object!=ANY: # subject+predicate+object is given
if object in subjectDictionary[predicate]:
yield (subject, predicate, object), self.__contexts()
else: # given object not found
pass
else: # subject+predicate is given, object unbound
for o in subjectDictionary[predicate].keys():
yield (subject, predicate, o), self.__contexts()
else: # given predicate not found
pass
else: # subject given, predicate unbound
for p in subjectDictionary.keys():
if object!=ANY: # object is given
if object in subjectDictionary[p]:
yield (subject, p, object), self.__contexts()
else: # given object not found
pass
else: # object unbound
for o in subjectDictionary[p].keys():
yield (subject, p, o), self.__contexts()
else: # given subject not found
pass
elif predicate!=ANY: # predicate is given, subject unbound
pos = self.__pos
if predicate in pos:
predicateDictionary = pos[predicate]
if object!=ANY: # predicate+object is given, subject unbound
if object in predicateDictionary:
for s in predicateDictionary[object].keys():
yield (s, predicate, object), self.__contexts()
else: # given object not found
pass
else: # predicate is given, object+subject unbound
for o in predicateDictionary.keys():
for s in predicateDictionary[o].keys():
yield (s, predicate, o), self.__contexts()
elif object!=ANY: # object is given, subject+predicate unbound
osp = self.__osp
if object in osp:
objectDictionary = osp[object]
for s in objectDictionary.keys():
for p in objectDictionary[s].keys():
yield (s, p, object), self.__contexts()
else: # subject+predicate+object unbound
spo = self.__spo
for s in spo.keys():
subjectDictionary = spo[s]
for p in subjectDictionary.keys():
for o in subjectDictionary[p].keys():
yield (s, p, o), self.__contexts()
def __len__(self, context=None):
#@@ optimize
i = 0
for triple in self.triples((None, None, None)):
i += 1
return i
def bind(self, prefix, namespace):
self.__prefix[namespace] = prefix
self.__namespace[prefix] = namespace
def namespace(self, prefix):
return self.__namespace.get(prefix, None)
def prefix(self, namespace):
return self.__prefix.get(namespace, None)
def namespaces(self):
for prefix, namespace in self.__namespace.iteritems():
yield prefix, namespace
def __contexts(self):
return (c for c in []) # TODO: best way to return empty generator
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