from py2neo import authenticate, Graph, Node, Relationship
authenticate("localhost:7474", "neo4j", "<pass>")
graph = Graph()

You have to make sure your Neo4j Database exists at localhost:7474 with the appropriate credentials.

the graph object is your interface to the neo4j instance in the rest of your python code. Rather thank making this a global variable, you should keep it in a class’s __init__ method.