Setting cardinality in gremlin-python

[Tharidu Fernando]

Hi all,

I'm trying to set a list vertex property using Cardinality.

This is possible in gremlin console using,

v.property(list, 'name', 'm. a. rodriguez')

v.property(list, 'name', 'marko')

I cannot figure out how to do this using gremling-python library. Any help will be appreciated!

Thanks

[David Brown]

Hi Tharidu,

Here is an example interpreter session:

[1]: from gremlin_python.structure import graph

[2]: from gremlin_python.driver.driver_remote_connection import DriverRemoteConnection

[3]: from gremlin_python.process.traversal import Cardinality

[4]: driver = DriverRemoteConnection('ws://localhost:8182/gremlin', 'g')

[5]: g = graph.Graph().traversal().withRemote(driver)

[6]: g.addV('person').property(Cardinality.list_, 'name', 'm. a. rodriguez').property(Cardinality.list_, 'name', 'marko').next()

Out[6]: v[0]

[7]: g.V(0).properties('name').toList()

Out[7]: [vp[name->m. a. rodriguez], vp[name->marko]]

Hope that helps.

Best,

Dave

[Tharidu Fernando]

Hi Dave,

Thanks for the help. Unfortunately, Gremlin server does not support saving lists as a property in Neo4j implementation (which I'm using), so I have to rethink on a better way of storing it.

But this works for in-memory Tinkerpop graph implementation.

Thank you,

Best regards,

Tharidu

[Tharidu Fernando]

An update on Neo4j. I've somehow missed that multi-properties should be enabled manually for Neo4j. Reference

After enabling multi-properties, now it's working as intended.

[Dirk Reiners]

Sorry for reviving an old thread, but I'm running into the same problem...

Does this solution still work for anybody? When I try it I get "gremlin_python.driver.protocol.GremlinServerError: 500: Key is defined for SINGLE cardinality which conflicts with specified: list", which is unfortunately the same that I get in my own code...

Is there an alternative to create a property with multiple values in gremlin-python? I tried .property(Cardinality.list_, 'name', 'm. a. rodriguez', 'name', 'marko'), but that doesn't work either.

Any input welcome!

  Dirk

[Stephen Mallette]

I'm pretty sure that the error message comes from JanusGraph:

https://github.com/JanusGraph/janusgraph/blob/8c492b0e29dad1f4754b5690eef4da94a33e2d75/janusgraph-core/src/main/java/org/janusgraph/graphdb/transaction/StandardJanusGraphTx.java#L750

and it's simply related to your schema definition. I think you just need to be sure that the property you are setting is configured to allow for list.

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[Dirk Reiners]

Good point, thanks for pointing that out! So far I've only used the automatic schema. 

Now I need to figure out how to do that in a reproducible manner, and why my gremlin shell complains about 'gremlin-groovy is not an available GremlinScriptEngine'. But those are different threads...

Thanks!