Getting started

Connecting

Before executing any neomodel code set the connection url:

from neomodel import config
config.DATABASE_URL = 'bolt://neo4j:neo4j@localhost:7687'  # default

This needs to be called early on in your app, if you are using Django the settings.py file is ideal.

If you are using your neo4j server for the first time you will need to change the default password. This can be achieved by visiting the neo4j admin panel (default: http://localhost:7474 ).

You can also change the connection url at any time by calling set_connection:

from neomodel import db
db.set_connection('bolt://neo4j:neo4j@localhost:7687')

The new connection url will be applied to the current thread or process.

Definition

Below is a definition of two types of node Person and Country:

from neomodel import (config, StructuredNode, StringProperty, IntegerProperty,
    UniqueIdProperty, RelationshipTo, RelationshipFrom)

config.DATABASE_URL = 'bolt://neo4j:password@localhost:7687'

class Country(StructuredNode):
    code = StringProperty(unique_index=True, required=True)

    # traverse incoming IS_FROM relation, inflate to Person objects
    inhabitant = RelationshipFrom('Person', 'IS_FROM')


class Person(StructuredNode):
    uid = UniqueIdProperty()
    name = StringProperty(unique_index=True)
    age = IntegerProperty(index=True, default=0)

    # traverse outgoing IS_FROM relations, inflate to Country objects
    country = RelationshipTo(Country, 'IS_FROM')

There is one type of relationship present IS_FROM, we are defining two different ways for traversing it one accessible via Person objects and one via Country objects

We can use the Relationship class as opposed to the RelationshipTo or RelationshipFrom if we don’t want to specify a direction.

Neomodel automatically creates a label for each StructuredNode class in the database
with the corresponding indexes and constraints.

Setup constraints and indexes

After creating node definitions in python, any constraints or indexes need to be added to Neo4j.

Neomodel provides a script to automate this:

$ neomodel_install_labels yourapp.py someapp.models --db bolt://neo4j:neo4j@localhost:7687

It is important to execute this after altering the schema. Keep an eye on the number of classes it detects each time.

Create, Save, Delete

Using convenient methods:

jim = Person(name='Jim', age=3).save()
jim.age = 4
jim.save() # validation happens here
jim.delete()
jim.refresh() # reload properties from neo
jim.id # neo4j internal id

Finding nodes

Using the ‘.nodes’ class property:

# raises Person.DoesNotExist if no match
jim = Person.nodes.get(name='Jim')

# Will return None unless bob exists
someone = Person.nodes.get_or_none(name='bob')

# Return set of nodes
people = Person.nodes.filter(age__gt=3)

Relationships

Working with relationships:

germany = Country(code='DE').save()
jim.country.connect(germany)

if jim.country.is_connected(germany):
    print("Jim's from Germany")

for p in germany.inhabitant.all()
    print(p.name) # Jim

len(germany.inhabitant) # 1

# Find people called 'Jim' in germany
germany.inhabitant.search(name='Jim')

jim.country.disconnect(germany)