How to create an OpenSplice DDS topic using python and statically created topic classes?

Question

I've been trying to use ADLINK's Vortex OpenSplice Community edition with the Python API (python version 3.6 within a PyEnv virtual environment) on Ubuntu 20.04.2 LTS. I've followed the PythonDCPSAPIGuide and got the python examples in ($OSPL_HOME/tools/python/examples) working. However I can't figure out how to create a topic associated for a domain participant for a statically generated topic class using idlpp. How would I be able to do this?

What I have done so far:

---

I have an IDL file that has include paths for quite a few other IDL files. I have converted these IDL files to a python topic classes using the following bash script:

#!/bin/bash

for FILE in *.idl; do
  $OSPL_HOME/bin/idlpp -I $OSPL_HOME/etc/idl -S -l python -d . $FILE
done

This creates a series of python packages (python topic classes) that I import into my python script which is in the same directory.

Using these packages I would like to create or register a topic with a domain participant in my python script. For example something like the following python code, (however the 'create_topic' function doesn't exist):

# myExampleDDSFile.py

from dds import *
from foo import foo_type # idlpp generated module/class
from foo2 import foo_type2 # idlpp generated module/class

dp = DomainParticipant()
topic = dp.create_topic('foo_topic',foo_type) # this function doesn't exist for a domain participant
pub = dp.create_publisher()

Would this be possible and if so how would I be able to register a topic that I have statically created with a domain participant in python?

---

I noticed in the provided python examples (e.g. $OSPL_HOME/tools/python/examples/example1.py) a topic is registered dynamically using the following code below, but I don't think this relates to statically generated python topic classes:

# example1.py snippet

dp = DomainParticipant()
gen_info = ddsutil.get_dds_classes_from_idl('example1.idl', 'basic::module_SequenceOfStruct::SequenceOfStruct_struct')
topic = gen_info.register_topic(dp, 'Example1')

I also couldn't see a relevant function in the source code.

I apologise if this is a simple question or if I have missed something - I am very new to Vortex OpenSplice DDS.

Any help would be appreciated.

Answer 1

I can't speak to OpenSplice, but you can do this with CoreDX DDS. For example, given the IDL file "hello.idl":

struct StringMsg
{
   string msg;
};

run

coredx_ddl -l python -f hello.idl -d hello

And, then the following python is an example of how to use the generated 'StringMsg' type to construct a Topic and a DataReader:

import time
import dds.domain
from  hello import StringMsg

# Use default QoS, and no listener
dp    = dds.domain.DomainParticipant( 0 )
topic = dds.topic.Topic( StringMsg, "helloTopic", "StringMsg", dp )
sub   = dds.sub.Subscriber( dp )
dr    = dds.sub.DataReader( sub, topic )
rc    = dr.create_readcondition( dds.core.SampleState.ANY_SAMPLE_STATE,
                                 dds.core.ViewState.ANY_VIEW_STATE,
                                 dds.core.InstanceState.ANY_INSTANCE_STATE )
ws    = dds.cond.WaitSet()
ws.attach_condition(rc)

while True:
    t = dds.core.Duration.infinite()
    print('waiting for data...')
    ws.wait(t)
    while True:
        try:
            samples = dr.take( )
            for s in samples:
                if s.info.valid_data:
                    print("received: {}".format(s.data.msg))
        except dds.core.Error:
            break;