initBindings failure in 4.2.2

[d.c.so...@gmail.com]

Hello-

I'm trying to follow the newbie examples on readthedocs and need to be able to query with with a variable, but can't seem to figure out how. The examples given in 4.2.2 do not work.

Here I provide a simple failure case:

```
Hopefully I'm really misunderstanding the examples here...

Here is a sample test case:

from rdflib import Graph, Literal, BNode, Namespace, RDF, URIRef
from rdflib.namespace import DC, FOAF
from rdflib.plugins.sparql import prepareQuery

g = Graph()

# Create an identifier to use as the subject for Donna.
donna = BNode()

# Add triples using store's add method.
g.add( (donna, RDF.type, FOAF.Person) )
g.add( (donna, FOAF.nick, Literal("donna", lang="foo")) )
g.add( (donna, FOAF.name, Literal("Donna Fales")) )
g.add( (donna, FOAF.mbox, URIRef("mailto:do...@example.org")) )

print(g.serialize(format='nt'))

q = prepareQuery('SELECT ?hash WHERE { ?hash <http://xmlns.com/foaf/0.1/name> "Donna Fales" .}')
person = "Donna Fales"
q2 = prepareQuery('SELECT ?hash WHERE { ?hash <http://xmlns.com/foaf/0.1/name> ?person .}')

#
# Example query works
#
qres = g.query(q)
if qres:
print("Found ?hash equal to:")
print(qres.result)
#
# Example initBindings does not work
#
qres2 = g.query(q2, initBindings={'person': person})
if qres2:
print("Found ?hash equal to:")
print(qres2.result)
else:
print("{} not found in rdf - initBindings failed :(".format(person))
```

and the results:
```
_:N87622270e0574740bdea75e1bc609595 <http://xmlns.com/foaf/0.1/name> "Donna Fales" .
_:N87622270e0574740bdea75e1bc609595 <http://xmlns.com/foaf/0.1/mbox> <mailto:do...@example.org> .
_:N87622270e0574740bdea75e1bc609595 <http://xmlns.com/foaf/0.1/nick> "donna"@foo .
_:N87622270e0574740bdea75e1bc609595 <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://xmlns.com/foaf/0.1/Person> .

Found ?hash equal to:
[(rdflib.term.BNode('N87622270e0574740bdea75e1bc609595'),)]
Donna Fales not found in rdf - initBindings failed :(
[Finished in 0.805s]
```

While the above code demonstrates searching with explicit terms 2,3, in a triple (1, 2, 3) returns the expected corresponding triple, declaring x=3 and searching 2,x fails to return anything. This seems like a trivial example - what am I doing wrong?

The corresponding example in the documentation code (http://rdflib.readthedocs.io/en/stable/intro_to_sparql.html ) also fails, and I dont know where else to turn :(

Help!

[Gunnar Aastrand Grimnes]

I replied to your issue on github :)

You need to pass a Literal not a string.

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