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from fastapi import FastAPI, Query, Request, HTTPException
from fastapi.responses import JSONResponse, HTMLResponse
from rdflib import Graph
import os
import uvicorn
app = FastAPI(title="Cars Knowledge Graph SPARQL Endpoint")
# Load the Knowledge Graph
g = Graph()
GRAPH_FILE = "cars_knowledge_graph.ttl"
if os.path.exists(GRAPH_FILE):
print(f"Loading Knowledge Graph from {GRAPH_FILE}...")
g.parse(GRAPH_FILE, format="turtle")
print(f"Graph loaded with {len(g)} triples.")
else:
print(f"WARNING: {GRAPH_FILE} not found. Please run convert_data.py first.")
@app.get("/", response_class=HTMLResponse)
async def home():
return """
<h1>Cars Knowledge Graph SPARQL Endpoint (FastAPI)</h1>
<p>The Knowledge Graph is published and accessible.</p>
<p>Send SPARQL queries to: <code>/sparql</code></p>
<h3>Example Query:</h3>
<pre>
SELECT ?s ?p ?o WHERE { ?s ?p ?o } LIMIT 10
</pre>
<p>View API Docs at: <a href="/docs">/docs</a></p>
"""
async def run_query(query: str):
if not query:
raise HTTPException(status_code=400, detail="No query provided")
try:
results = g.query(query)
# Format results as JSON
res_list = []
for row in results:
res_dict = {}
if getattr(results, "vars", None):
for i, var in enumerate(results.vars):
if row[i] is not None:
res_dict[str(var)] = str(row[i])
res_list.append(res_dict)
return {"results": res_list}
except Exception as e:
raise HTTPException(status_code=500, detail=str(e))
@app.get("/sparql")
async def sparql_get(query: str = Query(..., description="SPARQL Query")):
return await run_query(query)
@app.post("/sparql")
async def sparql_post(request: Request):
# Handle both form data and raw body
content_type = request.headers.get("content-type", "")
if "application/x-www-form-urlencoded" in content_type:
form = await request.form()
query = form.get("query")
else:
# data = await request.json() # Optional depending on client
query = (await request.body()).decode("utf-8")
return await run_query(query)
if __name__ == "__main__":
print("Starting SPARQL Endpoint on http://localhost:8000")
uvicorn.run(app, host="0.0.0.0", port=8000)
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