reachable_from()#

relationalai.std.graphs.Compute
reachable_from(node: Producer) -> Expression

Find all nodes reachable from node in a graph. One node is reachable from another if there is a path from the first node to the second. Nodes with self-loops are considered to be reachable from themselves. Must be called in a rule or query context.

Supported Graph Types#

Graph TypeSupportedNotes
DirectedYes
UndirectedYes
WeightedYesWeights are ignored.
UnweightedYes

Parameters#

NameTypeDescription
nodeProducerA node in the graph.

Returns#

Returns an Expression object that produces model objects that are reachable from node.

Example#

Use .reachable_from() to find all nodes reachable from a node in a graph. You access the .reachable_from() method from a Graph object’s .compute attribute:

import relationalai as rai
from relationalai.std.graphs import Graph

# Create a model named "socialNetwork" with a Person type.
model = rai.Model("socialNetwork")
Person = model.Type("Person")

# Add some people to the model and connect them with a multi-valued `follows` property.
with model.rule():
    alice = Person.add(name="Alice")
    bob = Person.add(name="Bob")
    carol = Person.add(name="Carol")
    alice.follows.add(bob)
    bob.follows.add(carol)

# Create a directed graph with Person nodes and edges between followers.
# Note that graphs are directed by default.
# This graph has edges from Alice to Bob and Bob to Carol.
graph = Graph(model)
graph.Node.extend(Person)
graph.Edge.extend(Person.follows)

# Who is reachable from Alice?
with model.query() as select:
    reachable = graph.compute.reachable_from(Person(name="Alice"))
    response = select(reachable.name)

print(response.results)
# Output:
#     name
# 0    Bob
# 1  Carol

In the example above, both Bob and Carol are reachable from Alice because there is a path from Alice to Bob and a path from Alice to Carol that passes through Bob. Alice is not reachable from herself because her node has no self-loop.

To check if one node is reachable from another, use .is_reachable(). Use .distance() to find the shortest path length between two nodes.

See Also#