data = """
@prefix rdf:  <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
@prefix foaf: <http://xmlns.com/foaf/0.1/> .
@base <http://my.org/> .
@prefix : <#> .

:club1 foaf:name "SC Floridsdorf" .
:club2 foaf:name "SC Leopoldsstadt" .
:player1 foaf:name "Hugo Muster" .
:player1 :member :club1 .
:player2 foaf:name "Fritz Wepper" .
:player2 :member :club2 .
:player1 :white :game1 .
:player2 :black :game1 .
:game1 :winner :white .
"""

import rdflib

g = rdflib.Graph()
g.parse(data=data, format='turtle')
print(len(g))

9

# list of winners

q = """
SELECT ?name WHERE { 
  ?game :winner ?color .
  ?player ?color ?game .
  ?player foaf:name ?name 
  }
"""

for row in g.query(q):
    print(row['name'])

Hugo Muster