RDFlib查询不起作用

时间：2018-03-13 11:25:48

标签： python sparql dbpedia rdflib

我编写了一个Python脚本，该脚本应该能够运行dbpedia URI列表并对它们运行查询。但是，出于某种原因，我在

上收到错误 
qres = g.query(query)

当我运行此代码时。有谁知道为什么会发生这种情况以及如何解决这个问题？我真的陷入了困境，而且我在论文时间表上落后了，所以压力确实在增加。

代码：

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：）

修改

我认为

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

此示例中尝试解析的URI是＆＃34; http://dbpedia.org/resource/Sheldon_J._Plankton＆＃34;

如果我直接将该URI放在g.parse中，

也会出错。这可能是因为URI是＃34;错误＆＃34;，因为它重定向到

＆＃34; http://dbpedia.org/resource/Plankton_(character)＆＃34 ;.

我在dbo：wikiPageRedirects的查询中解决了这个问题，但当然这是在解析之后。所以问题就在于我认为，但是如果我不能首先解析它来获取该页面，我怎么能使用dbo获取正确的页面：wikiPageRedirects？

1 个答案:

答案 0 :(得分：3)

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是一个dbpedia资源并且只包含URI的最后部分（即“Sheldon_J._Plankton”），那么获取重定向页面的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，则此查询应该有效。但您可能需要在上一个查询中返回的URI上运行g.parse，以将其添加到您的数据中：

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