Create nodes and relationships in Neo4j using Python

Overview:

Nodes and the relationships between them form a graph. There may not be any relationship at all in a graph.
In graph theory nodes are also called as vertexes and the relationships are called as edges.
In the property graph model provided by Neo4j, nodes and relationships can have a number of labels and properties.
A property is a name value pair.
The Cypher Query Language (CQL) provides a powerful syntax through which nodes and relationships can be created on a Neo4j database.

Creating graphs on Neo4j database through Python:

Using the Neo4j Python driver (neo4j-driver) a Python program can create, manipulate and analyze the graphs on a Neo4j graph database.
After importing the GraphDatabase module the first step in connecting to the Neo4j database is to create a driver instance.
The driver instance takes care of managing the connection pool required for the application, which can be controlled through parameters like MaxConnectionPoolSize.
The Python example program below creates a set of nodes representing some of the Ivy League universities and the distance between them in miles.

Creating nodes and relationships in a Neo4j graph

Through the session object obtained from the driver the CQL command is sent to the Neo4j server, which creates the university nodes and the distance relationships between them.

Example:

# import the neo4j driver for Python

from neo4j.v1 import GraphDatabase

# Database Credentials

uri = "bolt://localhost:7687"

userName = "neo4j"

password = "test"

# Connect to the neo4j database server

graphDB_Driver = GraphDatabase.driver(uri, auth=(userName, password))

# CQL to query all the universities present in the graph

cqlNodeQuery = "MATCH (x:university) RETURN x"

# CQL to query the distances from Yale to some of the other Ivy League universities

cqlEdgeQuery = "MATCH (x:university {name:'Yale University'})-[r]->(y:university) RETURN y.name,r.miles"

# CQL to create a graph containing some of the Ivy League universities

cqlCreate = """CREATE (cornell:university { name: "Cornell University"}),

(yale:university { name: "Yale University"}),

(princeton:university { name: "Princeton University"}),

(harvard:university { name: "Harvard University"}),

(cornell)-[:connects_in {miles: 259}]->(yale),

(cornell)-[:connects_in {miles: 210}]->(princeton),

(cornell)-[:connects_in {miles: 327}]->(harvard),

(yale)-[:connects_in {miles: 259}]->(cornell),

(yale)-[:connects_in {miles: 133}]->(princeton),

(yale)-[:connects_in {miles: 133}]->(harvard),

(harvard)-[:connects_in {miles: 327}]->(cornell),

(harvard)-[:connects_in {miles: 133}]->(yale),

(harvard)-[:connects_in {miles: 260}]->(princeton),

(princeton)-[:connects_in {miles: 210}]->(cornell),

(princeton)-[:connects_in {miles: 133}]->(yale),

(princeton)-[:connects_in {miles: 260}]->(harvard)"""

# Execute the CQL query

with graphDB_Driver.session() as graphDB_Session:

# Create nodes

graphDB_Session.run(cqlCreate)

# Query the graph

nodes = graphDB_Session.run(cqlNodeQuery)

print("List of Ivy League universities present in the graph:")

for node in nodes:

print(node)

# Query the relationships present in the graph

nodes = graphDB_Session.run(cqlEdgeQuery)

print("Distance from Yale University to the other Ivy League universities present in the graph:")

for node in nodes:

print(node)

Output:

List of Ivy League universities present in the graph:

Distance from Yale University to the other Ivy League universities present in the graph: