cannot reproduce bulbs/py2neo in python to create edges (relationships)

Question

I am trying to sequentially insert vertices and edges in neo4j using python. The existing nodes aren't recognised as such when I add edges. Whether I use py2neo or bulbs I got a similar error message.

Note I am working with: linux64 python2.7 bulbs0.3 py2neo1.5 neo4j-community1.8.2

With bulbs:

>>> from bulbs.neo4jserver import Graph
>>> g = Graph()
>>> g.vertices.create(name="James")
>>> g.vertices.create(name="Julie")
>>> g.edges.create(james, "knows", julie)

---------------------------------------------------------------------------
NameError                                 Traceback (most recent call last)
<ipython-input-46-9ba24256218d> in <module>()
----> 1 g.edges.create(james, "knows", julie)

NameError: name 'james' is not defined

With py2neo

from py2neo import neo4j
graph=neo4j.GraphDatabaseService()
node=graph.create({"name":'James'},{'name':'Julie'})
rel=graph.create((james,"knows",julie))
---------------------------------------------------------------------------
NameError                                 Traceback (most recent call last)
<ipython-input-8-591f826cfd05> in <module>()
      2 graph=neo4j.GraphDatabaseService()
      3 node=graph.create({"name":'James'},{'name':'Julie'})
----> 4 rel=graph.create((james,"knows",julie))

NameError: name 'james' is not defined

Moreover I got the same error with bulbs if I use rexster instead of neo4j, i.e.

>>> from bulbs.rexster import Graph
>>> g = Graph()
>>> g.vertices.create(name="James")
>>> g.vertices.create(name="Julie")
>>> g.edges.create(james, "knows", julie)
---------------------------------------------------------------------------
NameError                                 Traceback (most recent call last)
<ipython-input-6-2cfb5faa42d1> in <module>()
      3 g.vertices.create(name="James")
      4 g.vertices.create(name="Julie")
----> 5 g.edges.create((james, "knows", julie))

NameError: name 'james' is not defined

What's wrong here?

Thanks

score 2 · Accepted Answer · answered Apr 27 '13 at 14:21

Your application variables james and julie won't automatically be created simply by creating nodes with a similar name property. You haven't shared any of your py2neo code and I'm not familiar with bulbs but within py2neo you will need to do something like:

from py2neo import neo4j
graph_db = neo4j.GraphDatabaseService()
james, julie = graph_db.create(node(name="James"), node(name="Julie"))
graph_db.create(rel(james, "KNOWS", julie))

You could of course instead create both nodes and relationship in the same statement (and batch) if you preferred:

from py2neo import neo4j
graph_db = neo4j.GraphDatabaseService()
james, julie, friendship = graph_db.create(
    node(name="James"), node(name="Julie"), rel(0, "KNOWS", 1)
)

score 1 · Answer 2 · answered May 16 '13 at 03:28

You're not setting the james or julie vars on your create statements.

Here's the proper code:

>>> from bulbs.neo4jserver import Graph
>>> g = Graph()
>>> james = g.vertices.create(name="James")
>>> julie = g.vertices.create(name="Julie")
>>> g.edges.create(james, "knows", julie)

See the Bulbs Quickstart for more examples.

cannot reproduce bulbs/py2neo in python to create edges (relationships)

2 Answers2