在rdflib中创建custom_function

Question

我正在尝试在 Python 中的 rdflib 中创建一个自定义函数，以便从 SPARQL 查询进行调用。

我创建了这个应该返回“test”的简单示例。它不会给出错误。它什么也没返回。

from rdflib import Graph, URIRef, Literal
from rdflib.plugins.sparql.operators import custom_function

g = Graph()

@custom_function(URIRef("http://example.org/myCustomFunction"))
def myCustomFunction(args):
    return Literal("test")

query = """
SELECT ?result WHERE {
    BIND(<http://example.org/myCustomFunction>() AS ?result)
}
"""

for row in g.query(query):
    print(f"Result: {row.result}")

希望大家能帮忙。

Answer 1

from rdflib import Graph, URIRef, Literal
from rdflib.plugins.sparql.operators import custom_function

g = Graph()

# Define the custom function
@custom_function(URIRef("http://example.org/myCustomFunction"))
def myCustomFunction(args):
return Literal("test")

# Bind the custom function to the graph
g.store.query.bind("http://example.org/myCustomFunction", myCustomFunction)

# Prepare and execute the SPARQL query
query = """
SELECT ?result WHERE {
BIND(<http://example.org/myCustomFunction>() AS ?result)
}
"""

# Associate the graph with the query
 result = g.query(query)

# Iterate through the results
for row in result:
   print(f"Result: {row.result}")