import itertools
import os
import shutil
import tempfile
import types
import warnings
from io import BytesIO
from typing import IO, TYPE_CHECKING, List, Optional, Union, cast
from urllib.parse import urlparse
__all__ = ["Processor", "Result", "ResultParser", "ResultSerializer", "ResultException"]
if TYPE_CHECKING:
from rdflib.graph import Graph
from rdflib.term import Variable
[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
http://bugs.python.org/issue11649
"""
def __init__(self, stream):
self.__stream = stream
def write(self, arg):
if isinstance(arg, str):
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((str(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 str(name) in self.labels: # passing in variable object
return tuple.__getitem__(self, self.labels[str(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_: str):
if type_ not in ("CONSTRUCT", "DESCRIBE", "SELECT", "ASK"):
raise ResultException("Unknown Result type: %s" % type_)
self.type = type_
self.vars: Optional[List["Variable"]] = None
self._bindings = None
self._genbindings = None
self.askAnswer: bool = None # type: ignore[assignment]
self.graph: "Graph" = None # type: ignore[assignment]
@property
def bindings(self):
"""
a list of variable bindings as dicts
"""
if self._genbindings:
self._bindings += list(self._genbindings)
self._genbindings = None
return self._bindings
@bindings.setter
def bindings(self, b):
if isinstance(b, (types.GeneratorType, itertools.islice)):
self._genbindings = b
self._bindings = []
else:
self._bindings = b
[docs] @staticmethod
def parse(
source=None,
format: Optional[str] = None,
content_type: Optional[str] = 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: Optional[Union[str, IO]] = None,
encoding: str = "utf-8",
format: str = "xml",
**args,
) -> Optional[bytes]:
"""
Serialize the query result.
The :code:`format` argument determines the Serializer class to use.
- csv: :class:`~rdflib.plugins.sparql.results.csvresults.CSVResultSerializer`
- json: :class:`~rdflib.plugins.sparql.results.jsonresults.JSONResultSerializer`
- txt: :class:`~rdflib.plugins.sparql.results.txtresults.TXTResultSerializer`
- xml: :class:`~rdflib.plugins.sparql.results.xmlresults.XMLResultSerializer`
:param destination: Path of file output or BufferedIOBase object to write the output to.
:param encoding: Encoding of output.
:param format: One of ['csv', 'json', 'txt', xml']
:param args:
:return: bytes
"""
if self.type in ("CONSTRUCT", "DESCRIBE"):
return self.graph.serialize( # type: ignore[return-value]
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:
streamb: BytesIO = BytesIO()
stream2 = EncodeOnlyUnicode(streamb)
serializer.serialize(stream2, encoding=encoding, **args) # type: ignore
return streamb.getvalue()
if hasattr(destination, "write"):
stream = cast(IO[bytes], destination)
serializer.serialize(stream, encoding=encoding, **args)
else:
location = cast(str, destination)
scheme, netloc, path, params, query, fragment = urlparse(location)
if netloc != "":
print(
"WARNING: not saving as location" + "is not a local file reference"
)
return None
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)
return None
[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
[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: Result):
self.result = result
[docs] def serialize(self, stream: IO, encoding: str = "utf-8", **kwargs):
"""return a string properly serialized"""
pass # abstract
