RDFlib查询不起作用

Question

我编写了一个Python脚本，该脚本应该能够运行dbpedia URI的列表并对其进行查询。 但是，由于某种原因，我在

qres = g.query(query) 

当我运行这段代码时。 有谁知道为什么会这样，我该如何解决？ 我真的被困住了，而且我在论文的时间表上落后了，所以压力真的越来越大了。

码：

import rdflib
import csv
import pandas as pd

colnames = ['Link']

list2 = pd.read_csv('C:/Users/Frank/Google Drive/Master Scriptie/testtest3.csv', sep=',', header=None, usecols=[2], names=colnames)
saved_column = list2.Link 
outputfile = open('C:/Users/Frank/Google Drive/Master Scriptie/code files/dbpedia_output/test_dataset_uri_subject.csv', 'w')

reader = csv.reader(saved_column)

g = rdflib.Graph()
for uri in reader:
    uri2 = "".join(str(x) for x in uri)
    uri2 = uri2[1:].rstrip()
    print (uri2)
    result = g.parse("http://dbpedia.org" + uri2)
    print (result)
    query = "SELECT ?subject WHERE {<http://dbpedia.org" + uri2 + "> dbo:wikiPageRedirects*/dct:subject ?subject .}"
    print ("query: " + query)
    qres = g.query(query)
    for singlerow in qres:
        subject_final = "%s" % singlerow
        outputfile.write("{0}, {1} \n".format(uri,subject_final)

cmd中的错误消息：

/resource/Sheldon_J._Plankton
[a rdfg:Graph;rdflib:storage [a rdflib:Store;rdfs:label 'IOMemory']].
query: SELECT ?subject WHERE {<http://dbpedia.org/resource/Sheldon_J._Plankton>
dbo:wikiPageRedirects*/dct:subject ?subject .}
Traceback (most recent call last):
  File "rdfimport.py", line 47, in <module>
    qres = g.query(query)
  File "C:\Users\Frank\AppData\Local\Programs\Python\Python36-32\lib\site-packag
es\rdflib\graph.py", line 1089, in query
    query_object, initBindings, initNs, **kwargs))
  File "C:\Users\Frank\AppData\Local\Programs\Python\Python36-32\lib\site-packag
es\rdflib\plugins\sparql\processor.py", line 75, in query
    query = translateQuery(parsetree, base, initNs)
  File "C:\Users\Frank\AppData\Local\Programs\Python\Python36-32\lib\site-packag
es\rdflib\plugins\sparql\algebra.py", line 764, in translateQuery
    q[1], visitPost=functools.partial(translatePName, prologue=prologue))
  File "C:\Users\Frank\AppData\Local\Programs\Python\Python36-32\lib\site-packag
es\rdflib\plugins\sparql\algebra.py", line 384, in traverse
    r = _traverse(tree, visitPre, visitPost)
  File "C:\Users\Frank\AppData\Local\Programs\Python\Python36-32\lib\site-packag
es\rdflib\plugins\sparql\algebra.py", line 345, in _traverse
    e[k] = _traverse(val, visitPre, visitPost)
  File "C:\Users\Frank\AppData\Local\Programs\Python\Python36-32\lib\site-packag
es\rdflib\plugins\sparql\algebra.py", line 345, in _traverse
    e[k] = _traverse(val, visitPre, visitPost)
  File "C:\Users\Frank\AppData\Local\Programs\Python\Python36-32\lib\site-packag
es\rdflib\plugins\sparql\algebra.py", line 339, in _traverse
    return [_traverse(x, visitPre, visitPost) for x in e]
  File "C:\Users\Frank\AppData\Local\Programs\Python\Python36-32\lib\site-packag
es\rdflib\plugins\sparql\algebra.py", line 339, in <listcomp>
    return [_traverse(x, visitPre, visitPost) for x in e]
  File "C:\Users\Frank\AppData\Local\Programs\Python\Python36-32\lib\site-packag
es\rdflib\plugins\sparql\algebra.py", line 345, in _traverse
    e[k] = _traverse(val, visitPre, visitPost)
  File "C:\Users\Frank\AppData\Local\Programs\Python\Python36-32\lib\site-packag
es\rdflib\plugins\sparql\algebra.py", line 339, in _traverse
    return [_traverse(x, visitPre, visitPost) for x in e]
  File "C:\Users\Frank\AppData\Local\Programs\Python\Python36-32\lib\site-packag
es\rdflib\plugins\sparql\algebra.py", line 339, in <listcomp>
    return [_traverse(x, visitPre, visitPost) for x in e]
  File "C:\Users\Frank\AppData\Local\Programs\Python\Python36-32\lib\site-packag
es\rdflib\plugins\sparql\algebra.py", line 339, in _traverse
    return [_traverse(x, visitPre, visitPost) for x in e]
  File "C:\Users\Frank\AppData\Local\Programs\Python\Python36-32\lib\site-packag
es\rdflib\plugins\sparql\algebra.py", line 339, in <listcomp>
    return [_traverse(x, visitPre, visitPost) for x in e]
  File "C:\Users\Frank\AppData\Local\Programs\Python\Python36-32\lib\site-packag
es\rdflib\plugins\sparql\algebra.py", line 345, in _traverse
    e[k] = _traverse(val, visitPre, visitPost)
  File "C:\Users\Frank\AppData\Local\Programs\Python\Python36-32\lib\site-packag
es\rdflib\plugins\sparql\algebra.py", line 339, in _traverse
    return [_traverse(x, visitPre, visitPost) for x in e]
  File "C:\Users\Frank\AppData\Local\Programs\Python\Python36-32\lib\site-packag
es\rdflib\plugins\sparql\algebra.py", line 339, in <listcomp>
    return [_traverse(x, visitPre, visitPost) for x in e]
  File "C:\Users\Frank\AppData\Local\Programs\Python\Python36-32\lib\site-packag
es\rdflib\plugins\sparql\algebra.py", line 345, in _traverse
    e[k] = _traverse(val, visitPre, visitPost)
  File "C:\Users\Frank\AppData\Local\Programs\Python\Python36-32\lib\site-packag
es\rdflib\plugins\sparql\algebra.py", line 339, in _traverse
    return [_traverse(x, visitPre, visitPost) for x in e]
  File "C:\Users\Frank\AppData\Local\Programs\Python\Python36-32\lib\site-packag
es\rdflib\plugins\sparql\algebra.py", line 339, in <listcomp>
    return [_traverse(x, visitPre, visitPost) for x in e]
  File "C:\Users\Frank\AppData\Local\Programs\Python\Python36-32\lib\site-packag
es\rdflib\plugins\sparql\algebra.py", line 345, in _traverse
    e[k] = _traverse(val, visitPre, visitPost)
  File "C:\Users\Frank\AppData\Local\Programs\Python\Python36-32\lib\site-packag
es\rdflib\plugins\sparql\algebra.py", line 347, in _traverse
    _e = visitPost(e)
  File "C:\Users\Frank\AppData\Local\Programs\Python\Python36-32\lib\site-packag
es\rdflib\plugins\sparql\algebra.py", line 142, in translatePName
    return prologue.absolutize(p)
  File "C:\Users\Frank\AppData\Local\Programs\Python\Python36-32\lib\site-packag
es\rdflib\plugins\sparql\sparql.py", line 374, in absolutize
    return self.resolvePName(iri.prefix, iri.localname)
  File "C:\Users\Frank\AppData\Local\Programs\Python\Python36-32\lib\site-packag
es\rdflib\plugins\sparql\sparql.py", line 357, in resolvePName
    raise Exception('Unknown namespace prefix : %s' % prefix)
Exception: Unknown namespace prefix : dct

提前致谢 ：）

编辑：

我相信这出了问题

result = g.parse("http://dbpedia.org" + uri2)

在此示例中，它尝试解析的URI是“ http://dbpedia.org/resource/Sheldon_J._Plankton ”

如果我直接将该URI放在g.parse中，也会产生错误。 可能是因为URI“错误”，因为它重定向到

“ http://dbpedia.org/resource/Plankton_(character） ”。

我使用dbo：wikiPageRedirects在查询中修复了此问题，但这当然是在解析之后。 所以问题就在我想的那儿，但是如果我不能先解析它就可以使用dbo：wikiPageRedirects获得正确的页面呢？

Answer 1

错误消息抱怨无法识别前缀dct ，RDFLib内置了dcterms ，或者您可以绑定自己的前缀：

from rdflib.namespace import DCTERMS, Namespace
g.bind("dct", DCTerms)
g.bind("dbo", Namespace("http://dbpedia.org/ontology/"))
g.bind("dbr", Namespace("http://dbpedia.org/resource/"))

假设uri2是dbpedia资源，并且仅包含URI的最后一部分（即“ Sheldon_J._Plankton”），那么用于获取重定向页面的SPARQL查询将变为：

q = "SELECT ?subject WHERE {{ dbr:{} dbo:wikiPageRedirects ?subject. }}".format
result = g.query(q(uri2))
for row in result:
    print(row.subject)

要获取重定向的主题，如果它在您的数据中，则此查询应该起作用。 但是您可能需要对上一个查询返回的URI运行g.parse才能将其添加到数据中：

q = "SELECT ?subject WHERE {{ dbr:{} dbo:wikiPageRedirects ?redirect. ?redirect dct:subject ?subject. }}".format
result = q.query(q(uri2))