Source code for rdflib.plugins.sparql.results.csvresults

"""

This module implements a parser and serializer for the CSV SPARQL result
formats

http://www.w3.org/TR/sparql11-results-csv-tsv/

"""

import codecs
import csv
from typing import IO

from rdflib import Variable, BNode, URIRef, Literal

from rdflib.query import Result, ResultSerializer, ResultParser


[docs]class CSVResultParser(ResultParser):
[docs] def __init__(self): self.delim = ","
[docs] def parse(self, source, content_type=None): r = Result("SELECT") if isinstance(source.read(0), bytes): # if reading from source returns bytes do utf-8 decoding source = codecs.getreader("utf-8")(source) reader = csv.reader(source, delimiter=self.delim) r.vars = [Variable(x) for x in next(reader)] r.bindings = [] for row in reader: r.bindings.append(self.parseRow(row, r.vars)) return r
[docs] def parseRow(self, row, v): return dict( (var, val) for var, val in zip(v, [self.convertTerm(t) for t in row]) if val is not None )
[docs] def convertTerm(self, t): if t == "": return None if t.startswith("_:"): return BNode(t) # or generate new IDs? if t.startswith("http://") or t.startswith("https://"): # TODO: more? return URIRef(t) return Literal(t)
[docs]class CSVResultSerializer(ResultSerializer):
[docs] def __init__(self, result): ResultSerializer.__init__(self, result) self.delim = "," if result.type != "SELECT": raise Exception("CSVSerializer can only serialize select query results")
[docs] def serialize(self, stream: IO, encoding: str = "utf-8", **kwargs): # the serialiser writes bytes in the given encoding # in py3 csv.writer is unicode aware and writes STRINGS, # so we encode afterwards import codecs stream = codecs.getwriter(encoding)(stream) # type: ignore[assignment] out = csv.writer(stream, delimiter=self.delim) vs = [self.serializeTerm(v, encoding) for v in self.result.vars] # type: ignore[union-attr] out.writerow(vs) for row in self.result.bindings: out.writerow( [self.serializeTerm(row.get(v), encoding) for v in self.result.vars] # type: ignore[union-attr] )
[docs] def serializeTerm(self, term, encoding): if term is None: return "" else: return term