Source code for rdflib.query

from __future__ import absolute_import
from __future__ import division
from __future__ import print_function

import os
import itertools
import shutil
import tempfile
import warnings
import types

from six import BytesIO
from six import PY2
from six import text_type
from six.moves.urllib.parse import urlparse

__all__ = ['Processor', 'Result', 'ResultParser', 'ResultSerializer',

[docs]class Processor(object): """ Query plugin interface. This module is useful for those wanting to write a query processor that can plugin to rdf. If you are wanting to execute a query you likely want to do so through the Graph class query method. """
[docs] def __init__(self, graph): pass
[docs] def query(self, strOrQuery, initBindings={}, initNs={}, DEBUG=False): pass
class UpdateProcessor(object): """ Update plugin interface. This module is useful for those wanting to write an update processor that can plugin to rdflib. If you are wanting to execute an update statement you likely want to do so through the Graph class update method. .. versionadded:: 4.0 """ def __init__(self, graph): pass def update(self, strOrQuery, initBindings={}, initNs={}): pass
[docs]class ResultException(Exception): pass
class EncodeOnlyUnicode(object): """ This is a crappy work-around for """ def __init__(self, stream): self.__stream = stream def write(self, arg): if isinstance(arg, text_type): self.__stream.write(arg.encode("utf-8")) else: self.__stream.write(arg) def __getattr__(self, name): return getattr(self.__stream, name) class ResultRow(tuple): """ a single result row allows accessing bindings as attributes or with [] >>> from rdflib import URIRef, Variable >>> rr=ResultRow({ Variable('a'): URIRef('urn:cake') }, [Variable('a')]) >>> rr[0] rdflib.term.URIRef(u'urn:cake') >>> rr[1] Traceback (most recent call last): ... IndexError: tuple index out of range >>> rr.a rdflib.term.URIRef(u'urn:cake') >>> rr.b Traceback (most recent call last): ... AttributeError: b >>> rr['a'] rdflib.term.URIRef(u'urn:cake') >>> rr['b'] Traceback (most recent call last): ... KeyError: 'b' >>> rr[Variable('a')] rdflib.term.URIRef(u'urn:cake') .. versionadded:: 4.0 """ def __new__(cls, values, labels): instance = super(ResultRow, cls).__new__( cls, (values.get(v) for v in labels)) instance.labels = dict((text_type(x[1]), x[0]) for x in enumerate(labels)) return instance def __getattr__(self, name): if name not in self.labels: raise AttributeError(name) return tuple.__getitem__(self, self.labels[name]) def __getitem__(self, name): try: return tuple.__getitem__(self, name) except TypeError: if name in self.labels: return tuple.__getitem__(self, self.labels[name]) if text_type(name) in self.labels: # passing in variable object return tuple.__getitem__(self, self.labels[text_type(name)]) raise KeyError(name) def get(self, name, default=None): try: return self[name] except KeyError: return default def asdict(self): return dict((v, self[v]) for v in self.labels if self[v] is not None)
[docs]class Result(object): """ A common class for representing query result. There is a bit of magic here that makes this appear like different Python objects, depending on the type of result. If the type is "SELECT", iterating will yield lists of ResultRow objects If the type is "ASK", iterating will yield a single bool (or bool(result) will return the same bool) If the type is "CONSTRUCT" or "DESCRIBE" iterating will yield the triples. len(result) also works. """
[docs] def __init__(self, type_): if type_ not in ('CONSTRUCT', 'DESCRIBE', 'SELECT', 'ASK'): raise ResultException('Unknown Result type: %s' % type_) self.type = type_ self.vars = None self._bindings = None self._genbindings = None self.askAnswer = None self.graph = None
def _get_bindings(self): if self._genbindings: self._bindings += list(self._genbindings) self._genbindings = None return self._bindings def _set_bindings(self, b): if isinstance(b, (types.GeneratorType, itertools.islice)): self._genbindings = b self._bindings = [] else: self._bindings = b bindings = property( _get_bindings, _set_bindings, doc="a list of variable bindings as dicts")
[docs] @staticmethod def parse(source=None, format=None, content_type=None, **kwargs): from rdflib import plugin if format: plugin_key = format elif content_type: plugin_key = content_type.split(";", 1)[0] else: plugin_key = 'xml' parser = plugin.get(plugin_key, ResultParser)() return parser.parse(source, content_type=content_type, **kwargs)
[docs] def serialize( self, destination=None, encoding="utf-8", format='xml', **args): if self.type in ('CONSTRUCT', 'DESCRIBE'): return self.graph.serialize( destination, encoding=encoding, format=format, **args) """stolen wholesale from graph.serialize""" from rdflib import plugin serializer = plugin.get(format, ResultSerializer)(self) if destination is None: stream = BytesIO() stream2 = EncodeOnlyUnicode(stream) serializer.serialize(stream2, encoding=encoding, **args) return stream.getvalue() if hasattr(destination, "write"): stream = destination serializer.serialize(stream, encoding=encoding, **args) else: location = destination scheme, netloc, path, params, query, fragment = urlparse(location) if netloc != "": print("WARNING: not saving as location" + "is not a local file reference") return fd, name = tempfile.mkstemp() stream = os.fdopen(fd, 'wb') serializer.serialize(stream, encoding=encoding, **args) stream.close() if hasattr(shutil, "move"): shutil.move(name, path) else: shutil.copy(name, path) os.remove(name)
[docs] def __len__(self): if self.type == 'ASK': return 1 elif self.type == 'SELECT': return len(self.bindings) else: return len(self.graph)
[docs] def __bool__(self): if self.type == 'ASK': return self.askAnswer else: return len(self) > 0
if PY2: __nonzero__ = __bool__
[docs] def __iter__(self): if self.type in ("CONSTRUCT", "DESCRIBE"): for t in self.graph: yield t elif self.type == 'ASK': yield self.askAnswer elif self.type == 'SELECT': # this iterates over ResultRows of variable bindings if self._genbindings: for b in self._genbindings: if b: # don't add a result row in case of empty binding {} self._bindings.append(b) yield ResultRow(b, self.vars) self._genbindings = None else: for b in self._bindings: if b: # don't add a result row in case of empty binding {} yield ResultRow(b, self.vars)
[docs] def __getattr__(self, name): if self.type in ("CONSTRUCT", "DESCRIBE") and self.graph is not None: return self.graph.__getattr__(self, name) elif self.type == 'SELECT' and name == 'result': warnings.warn( "accessing the 'result' attribute is deprecated." " Iterate over the object instead.", DeprecationWarning, stacklevel=2) # copied from __iter__, above return [(tuple(b[v] for v in self.vars)) for b in self.bindings] else: raise AttributeError( "'%s' object has no attribute '%s'" % (self, name))
[docs] def __eq__(self, other): try: if self.type != other.type: return False if self.type == 'ASK': return self.askAnswer == other.askAnswer elif self.type == 'SELECT': return self.vars == other.vars \ and self.bindings == other.bindings else: return self.graph == other.graph except: return False
[docs]class ResultParser(object):
[docs] def __init__(self): pass
[docs] def parse(self, source, **kwargs): """return a Result object""" pass # abstract
[docs]class ResultSerializer(object):
[docs] def __init__(self, result): self.result = result
[docs] def serialize(self, stream, encoding="utf-8", **kwargs): """return a string properly serialized""" pass # abstract