PLW2901 - Is addition assignment in with block problematic code? #3903

g += graph is an assignment in Python: it roughly performs g = g.__iadd__(graph) (falling back to __add__). Therefore the name introduced by with ... as g can be rebound to a different object, which is what PLW2901 is warning about.

It does not change which context manager's __exit__ is called; Python keeps that separately. The risk is that later statements in the block now operate on the replacement value, and code after the block sees that replacement because with does not create a scope.

For RDFLib Graph.__iadd__, if it returns the same graph object, this particular use is intentional and harmless. I would either make the intent explicit (for example, call the mutating method directly if there is a suitable one) or use a targeted # noqa: PLW2901. The rule is conservative because Ruff cannot prove the runtime return identity of an arbitrary __iadd__ implementation.