flask/neo4j prototype

app.py

'''
Creates an event with 2 choices and 2 ends and serves them at http://127.0.0.1:5000/event/1
Works with a running server of neo4j.com, a graph DB that uses Cypher query language

Based on: https://nicolewhite.github.io/neo4j-flask/
(some of the py2neo code is out of date, I replaced it with the new API)
(this mentions virtualenv, but in python 3 just use venv)

Packages:
flask
py2neo
(the link above uses more packages)
'''

from flask import Flask, render_template # web framework @ http://flask.pocoo.org/
from py2neo import Graph, Node, Relationship # neo4j python driver @ http://py2neo.org
from py2neo.ogm import GraphObject, Property, RelatedTo, RelatedObjects # driver object-graph mapping

app = Flask(__name__, template_folder='.') # the Flask app will find event.html template in current folder

## Schema and testing data ##
# (:event)-[:leads_to]->(:event)

graph = Graph()

# comment out if you get 'already exists'
# graph.schema.create_uniqueness_constraint('Event', 'id') # Event nodes must have unique id (but could have no id)

start = Node('Event', id=1, text='There is a thing') # Node with label 'Even' and properties 'id' and 'text'
end1 = Node('Event', id=2, text='The thing is no more')
end2 = Node('Event', id=3, text='The thing is grateful')

option1 = Relationship(start, 'LEADS_TO', end1, text='I sword it with my sword') # Relationship with label 'LEADS_TO' and property 'text'
option2 = Relationship(start, 'LEADS_TO', end2, text="I tell it it's pretty")

graph.merge(option1) # adds to DB (if doesn't already exist)
graph.merge(option2)

## Models ##
class Event(GraphObject):
	__primarykey__ = 'id'
	_id = Property('id') # used _id because python has id function. argument indicates that property name in DB is 'id'
	text = Property()
	next_events = RelatedTo('Event', 'LEADS_TO') # RelatedObjects object (collection of objects with given relationship)

	def find(_id):
		return Event.select(graph, int(_id)).first()

	def paths(self): # return list of tuples (choice, next_event_id)
		paths = list()
		_next = self.next_events # assign to _name just for ease
		for event in _next:
			option = _next.get(event, 'text') # gets value of relationship property 'text', like 'I sword it with my sword'
			path = (option, event._id)
			paths.append(path)
		return paths

## Views ##
# try going to http://127.0.0.1:5000/event/1
@app.route('/event/<_id>')
def event(_id):
	event = Event.find(_id)
	text = event.text
	paths = event.paths()
	return render_template('event.html', text=text, paths=paths) # server will serve event.html, and text and paths can be used in event.html

## Run ##
app.run(debug=True)

event.html

<p>
	{{ text }}
</p>
<ul>
	{% for option, next in paths %}
		<li>
			<a href="{{ url_for('event', _id=next) }}">
				{{ option }}
			</a>
		</li>
	{% endfor %}
</ul>