Gremlin Python Cannot run the event loop

Question

I am running Gremlin Python. Firstly, I did the installation in my local machine following these instructions here then I ran the code of this website here, but I got the following error at this bit:

    heading('SubgraphStrategy - just Texas airports')
    strategy = SubgraphStrategy(vertices=__.has("region","US-TX"), edges=__.hasLabel('route'))
    g2 = g.withStrategies(strategy)
    verts = g2.V().count().next()

RuntimeError: Cannot run the event loop while another loop is running

I verified my connection to a graph database to Gremlin Server, with the following code

%%graph_notebook_config
{
  "host": "localhost",
  "port": 8182,
  "ssl": false,
  "gremlin": {
    "traversal_source": "g"
  }
}

I found some solutions to the "RuntimeError: Cannot run the event loop while another loop is running", like the nest_async, but then I got a different error.

Thank you

Kelvin Lawrence · Accepted Answer · 2022-07-30 23:40:43Z

6

If you are using Gremlin Python, inside a Jupyter notebook then an event loop will already be running. The 3.5.x and 3.6.x Gremlin Python clients have an option you can specify when you create your client object that will enable this to work. All you should need to do is something like this:

from gremlin_python.driver.aiohttp.transport import AiohttpTransport

# other common imports not shown

connection = DriverRemoteConnection(endpoint,'g',
                 transport_factory=lambda:AiohttpTransport(call_from_event_loop=True))

g = traversal().withRemote(connection)

edited Jul 30, 2022 at 23:40

answered Jul 29, 2022 at 23:42

Kelvin Lawrence

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7 Comments

Aureon Over a year ago

Hi Kelvin, thank you I did the correction, but I got this error: NameError: name 'AiohttpTransport' is not defined after this query verts = g2.V().count().next()

Kelvin Lawrence Over a year ago

Which version of the Gremlin Python are you using? The example I shared needs at least the 3.5.0 version.

Aureon Over a year ago

Hi Kelvin, gremlinpython==3.6.0, the other libraries are: graph-notebook==3.5.3 graphql-core==3.2.1. If you agree I can mark this answer as correct and I will make another post with the entire code as probably I am missing something.

Kelvin Lawrence Over a year ago

Yes, please. The answer as written should solve the event loop error.

Kelvin Lawrence Over a year ago

You also need to add an import though for from gremlin_python.driver.aiohttp.transport import AiohttpTransport - I will add that to the answer

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