Hello World doesn't output to Logstash

[eStrux-MAB]

I have a Logstash conf file configured as such:

    input {
        exec {
            command => "/etc/logstash/scripts/do_something.py"
            interval => 60
        }
    }

    output {
        stdout {}
    }

The executed Python script is as follows:

    print('Hello world!')

That's it. As bog-standard and as straightforward as this. And now, here's what actually lands into the stdout console when I monitor Logstash's logging:

    Apr  7 14:05:34 myhostname logstash: {
    Apr  7 14:05:34 myhostname logstash: "host" => "myhostname.mydomain.com",
    Apr  7 14:05:34 myhostname logstash: "command" => "/etc/logstash/scripts/do_something.py",
    Apr  7 14:05:34 myhostname logstash: "@timestamp" => 2020-04-07T18:05:34.781Z,
    Apr  7 14:05:34 myhostname logstash: "message" => "",
    Apr  7 14:05:34 myhostname logstash: "@version" => "1"
    Apr  7 14:05:34 myhostname logstash: }

For whatever reason I don't understand, the execution completes successfully, but the words "Hello World!" aren't present at all. Yet, if I run the Python script standalone, "Hello World!" does output to the console as normal.

Meanwhile, I have several other Logstash pipelines and Python scripts that are much more elaborate and output what shows up in stdout to various destinations, and they work 100%.

Obviously I must be doing something dead wrong in what turns out to be no more than the most basic of tests. I must've been banging myself against this for far too long, because I can't for the life of me figure out what's going on. I had begun with a slightly modified copy of another pipeline/script to test some error handling, and in trying to figure out the root cause of why my test wouldn't output anything, stripped it down until I was reduced to... this. A plain simple Hello World that should be foolproof, yet, go figure... isn't.

Any insight would be greatly appreciated.