The labels magic attribute

In NetworkX and Grand graph objects, there is no canonical way to "type" a vertex or edge. In Cypher, this is done with labels. For example, a node may have the label :Person or :Book, and an edge may have the label [:AUTHORED].

By convention, this repository uses the __labels__ attribute on a vertex to store the labels of a node. This is an iterable of strings. The __labels__ attribute is not required, but if it is present, it can be used in queries:

from grandcypher import GrandCypher
import networkx as nx

G = nx.Graph()
G.add_node(1, name="Douglas Adams", __labels__=["Person"])
G.add_node(2, name="The Hitchhiker's Guide to the Galaxy", __labels__=["Book"])
G.add_edge(1, 2, __labels__=["AUTHORED"])

GrandCypher(G).run("""
MATCH (a:Person)-[e]->(b:Book)
RETURN a.name, b.name
""")

Data IO

The grand-cypher-io repository provides a set of tools for reading and writing graphs in OpenCypher format.

The __labels__ attribute on nodes and edges will be automatically used to populate the "labels" attribute of the node for the purposes of writing to an OpenCypher file.

Likewise, the __labels__ attribute is used to populate the labels attribute of a node when reading from an OpenCypher file.