Bulbs: How to check if two vertices are connected by an edge in Titan - groovy

Question

I am using TitanGraphDB + Cassandra.I am starting Titan as follows
cd titan-cassandra-0.3.1
bin/titan.sh config/titan-server-rexster.xml config/titan-server-cassandra.properties
I have a Rexster shell that I can use to communicate to Titan+Cassandra above.
cd rexster-console-2.3.0
bin/rexster-console.sh
I am attempting to model a network topology using Titan Graph DB.I want to program the Titan Graph DB from my python program.I am using bulbs package for that.
I create three types of vertices
- switch
- port
- device
I create labelled edges between ports that are connected physically.The label that I use is "link".
Let us say I have two port vertices portA and portB.
I want to write a function as below
def is_connected(portA, portB):
...
...
...
How do I find if two vertices are "connected by a labelled edge"?
I have two graph vertices
src_sw_other_ports
<Vertex: http://localhost:8182/graphs/graph/vertices/48>
dst_sw_other_ports
<Vertex: http://localhost:8182/graphs/graph/vertices/72>
I have tried
link_exists = src_sw_other_ports.out.retain([dst_sw_other_ports]).hasNext()
It is giving me the following error.
File "/home/karthik/Projects/ryu/ryu/app/simple_switch.py", line 238, in compute_path
link_exists = src_sw_other_ports.out.retain([dst_sw_other_ports]).hasNext()
File "/usr/local/lib/python2.7/dist-packages/bulbs/element.py", line 209, in __getattr__
raise AttributeError(name)
AttributeError: out

Answer 1

espeed's answer is good. Here's another alternative:
gremlin> g = TinkerGraphFactory.createTinkerGraph()
==>tinkergraph[vertices:6 edges:6]
gremlin> v1 = g.v(1)
==>v[1]
gremlin> v3 = g.v(3)
==>v[3]
gremlin> v6 = g.v(6)
==>v[6]
gremlin> v1.out.retain([v3]).hasNext()
==>true
gremlin> v1.out.retain([v6]).hasNext()
==>false
A little better than using count as if you just want "existence" of an edge, you don't have to iterate the entire pipe to do so.

Answer 2

def is_connected(portA, portB):
return portA.both("link").retain([portB]).hasNext()
See http://gremlindocs.com/#recipes/finding-edges-between-vertices
NB: I used your function definition in the code above; however, your function definition uses Python syntax, not Groovy, so the above example will only work if you are calling the Gremlin code from Jython.
The Gremlin-Groovy definition would be:
def isConnected (portA, portB) {
return portA.both("link").retain([portB]).hasNext()
}