def _check_can_be_instantiated(cls, cache_location):
"""Pre-conditions: the cache location is the URL to a Fuseki server
and the SPARQLWrapper library exists (transitive dependency of
RDFlib's sparqlstore).
"""
if not any(
cache_location.startswith(prefix)
for prefix in cls._CACHE_URL_PREFIXES):
raise InvalidCacheException('cache location is not a Fuseki url')
try:
from rdflib.plugins.stores.sparqlstore import SPARQLUpdateStore
except ImportError:
raise InvalidCacheException('unable to import sparql store')
del SPARQLUpdateStore
def open(self):
"""Opens an existing cache.
"""
try:
self.graph.open(self.cache_uri, create=False)
self._add_namespaces(self.graph)
self.is_open = True
except Exception:
raise InvalidCacheException('The cache is invalid or not created')
def _check_can_be_instantiated(cls):
try:
from bsddb import db
except ImportError:
try:
from bsddb3 import db
except ImportError:
db = None
if db is None:
raise InvalidCacheException('no install of bsddb/bsddb3 found')
del db