sparql query with special characters to dbpedia returns 400 in python

Question

hi every one

i have a query in python, which requests an sparql query to dbpedia.

i want to get triples with special object.

here is my query:

query='''
            PREFIX rs: <http://dbpedia.org/resource/>
            PREFIX  dbo:  <http://dbpedia.org/ontology/>
            PREFIX  dbp:  <http://dbpedia.org/property/>
            
            select distinct ?sub,?predicate
            where
            {{
            ?sub ?predicate  rs:{a1}.
            }}
            
            '''.format(a1=ent)

url = 'https://dbpedia.org/sparql/'

myobj = {"query":query, "format":"json", "default-graph-uri":"http://dbpedia.org"}

try:
     r=requests.get(url, params=myobj) 

except  Exception as ex: 

     print("error for question for entity:"+ent+" : ",ex)

but the problem is when my object has special characters, i get 400 from dbpedia.

here is some examples that had bad request.

error for question for entity:Off_Limits_(1988_film) :  Expecting value: line 1 column 1 (char 0)
error for question for entity:Faith_of_My_Fathers_(film) :  Expecting value: line 1 column 1 (char 0)
error for question for entity:A_Rumor_of_War_(miniseries) :  Expecting value: line 1 column 1 (char 0)
error for question for entity:Bat*21 :  Expecting value: line 1 column 1 (char 0)
error for question for entity:Hearts_and_Minds_(film) :  Expecting value: line 1 column 1 (char 0)
error for question for entity:The_Green_Berets_(film) :  Expecting value: line 1 column 1 (char 0)
error for question for entity:War_in_Vietnam_(1954–59) :  Expecting value: line 1 column 1 (char 0)
error for question for entity:Alice's_Restaurant_(film) :  Expecting value: line 1 column 1 (char 0)
error for question for entity:Sir!_No_Sir! :  Expecting value: line 1 column 1 (char 0)
error for question for entity:Jacob's_Ladder_(film) :  Expecting value: line 1 column 1 (char 0)
error for question for entity:List_of_allied_military_operations_of_the_Vietnam_War_(1973–74) :  Expecting value: line 1 column 1 (char 0)
error for question for entity:War_in_Vietnam_(1945–46) :  Expecting value: line 1 column 1 (char 0)
error for question for entity:The_War_at_Home_(film) :  Expecting value: line 1 column 1 (char 0)
error for question for entity:Missing_in_Action_(film) :  Expecting value: line 1 column 1 (char 0)

<Response [400]>
error for question for entity:Off_Limits_(1988_film) :  Expecting value: line 1 column 1 (char 0)

so how can i request to dbpedia in python correctly?

Answer 1

You may also find rdflib useful for working with SPARQL queries in Python. Using it to pre-bind variables in a query can help in getting the syntax details correct and it will also help avoid potential problems with SPARQL injection .

Here is an example:

import rdflib

ent = "Off_Limits_(1988_film)"

obj = rdflib.URIRef(ent, base="http://dbpedia.org/resource/")
q = """
    SELECT DISTINCT ?sub ?pred
    WHERE {
        SERVICE <http://dbpedia.org/sparql> {
            ?sub ?pred ?obj .
        }
    }
    """
for row in rdflib.Graph().query(q, initBindings={"obj": obj}):
    print(str(row.sub), str(row.pred))

See also prepared queries in the rdflib documentation.

Answer 2

Special characters in prefixed names in SPARQL need to be escaped by prepending a backslash character. See this for the allowed form of SPARQL local names.

So for example instead of rs:Off_Limits_(1988_film) you need to use rs:Off_Limits_\(1988_film\) in the query.

See this for an example query.