[PYTHON] [Neo4J] ④ Try to handle the graph structure with Cypher

A corner where you can try Neo4J for a long time.

If you master the recently opened query language Cypher for graph databases, you will be able to create and search graph structures. So let's get started with Cypher.

I tried using py2neo, which I put in the last time, as a companion. Installation via pip:

sudo pip install py2neo $ python -V Python 2.7.10

1) Batch processing with py2neo

A subtle non-DRY example (and it doesn't work) that was on the web was copied and corrected for the time being so that batch processing was possible:

test.py

from py2neo import Graph

graph = Graph("http://neo4j:yourpassword@:7474/db/data/")
statement = """
  MERGE (person:Person {name:{person_name}}) ON CREATE SET
    person.age = {person_age},
    person.sex = {person_sex}

  MERGE (pet:Pet {name:{pet_name}}) ON CREATE SET
    pet.type = {pet_type}

  MERGE (person)-[:owns]->(pet)

  RETURN person
  """

tx = graph.cypher.begin()

persons = [
    {'name': 'Homer', 'age': 32, 'sex': 'Male', 'pet_name': 'Buller', 'pet_type': 'Dog'},
    {'name': 'Lucy', 'age': 12, 'sex': 'Male', 'pet_name': 'Buller', 'pet_type': 'Dog'},
    {'name': 'Lucy', 'age': 12, 'sex': 'Male', 'pet_name': 'Betty', 'pet_type': 'Cat'}
]

for person in persons:
    print person
    tx.append(statement, {
      'person_name': person['name'],
      'person_age': person['age'],
      'person_sex': person['sex'],

      'pet_name': person['pet_name'],
      'pet_type': person['pet_type']
    })

tx.process()

tx.commit()

You can see the flow by extracting only the transaction part:

tx = graph.cypher.begin() tx.append(statement, { ... }) tx.process() tx.commit()

Also, if you master the cypher syntax MERGE ~ ON CREATE in the statement, it looks pretty good.

See the example of py2neo committing JSON below, which could be written differently. http://jexp.github.io/blog/html/load_json.html

2) Write a query on the command line.

Next, try playing with cypher from the command line (environment is Mac).

$ neo4j-shell
Unable to find any JVMs matching version "1.7".
Welcome to the Neo4j Shell! Enter 'help' for a list of commands
NOTE: Remote Neo4j graph database service 'shell' at port 1337

neo4j-sh (?)$ MATCH (p)-[:owns]-(pet) WHERE p.name = "Lucy" RETURN p, pet;
+------------------------------------------------------------------------------+
| p                                       | pet                                |
+------------------------------------------------------------------------------+
| Node[11]{name:"Lucy",age:12,sex:"Male"} | Node[12]{name:"Betty",type:"Cat"}  |
| Node[11]{name:"Lucy",age:12,sex:"Male"} | Node[10]{name:"Buller",type:"Dog"} |
+------------------------------------------------------------------------------+
2 rows
46 ms

Something was complained when neo4j-shell was launched, but I was able to make a query.

3) Execute a query on the browser and graph it

Run the same query in your browser:

MATCH (p)-[:owns]-(pet) WHERE p.name = "Lucy" RETURN p, pet;

Press the Graph button on the right and you'll see the graph screen you expected: http://localhost:7474/browser/

4) cypher query cheat sheet, etc.

Below on the original site: http://neo4j.com/docs/stable/cypher-refcard/

I can't find a good introduction to Japanese on the web.

Hurry up and look forward to "study notes" with updates from time to time! http://qiita.com/Keech/items/6bd5b667e935a20be018

Let's do this at our own pace ^^;