Update graph operator overloading for subclasses by shreyasnagare · Pull Request #1349 · RDFLib/rdflib (original) (raw)

This PR makes the set operations for rdflib.Graph subclasses (like g1 = g1 + g2) more intuitive and similar to the results of in-place set operations (like g1 += g2).

Example:

If you were to do a union of a ConjunctiveGraph (a subclass of Graph) instance with itself or any other ConjunctiveGraph instance using something like g = g + g, the instance would lose all the methods specific to the ConjunctiveGraph.

Steps to reproduce the issue:

from rdflib import Graph

class MyGraph(Graph): def perform_reasoning(self): pass

g = MyGraph() "perform_reasoning" in dir(g)

True

g += g "perform_reasoning" in dir(g)

True

g = g + g "perform_reasoning" in dir(g)

False

Proposed Changes

• Use type(self)() instead of Graph() as the initial return value for set operations.
• This would allow Graph to pass down similar behavior to its derived classes (unless overridden) without breaking any existing functionality.