后台python进程的命令行界面

Question

How can I create a command line interface that persists as a background process and only executes commands when specific commands are entered? Please note the following is basically pseudo code:

def startup():
   # costly startup that loads objects into memory once in a background process

def tear_down()
   # shut down; generally not needed, as main is acting like a service

def main():
    startup()

    # pseudo code that checks shell input for a match; after execution releases back to shell
    while True:
        usr_in = get_current_bash_command()
        if usr_in == "option a":
            # blocking action that release control back to shell when complete
        if usr_in == "option b":
            # something else with handling like option a
        if usr_in == "quit":
            # shuts down background process; will not be used frequently
            tear_down()
            break
   print("service has been shut down.  Bye!")

if __name__ == "__main__":
    # run non-blocking in background, only executing code if usr_in matches commands:
    main()

Note what this is not:

• typical example of argparse or click, that runs a (blocking) python process until all commands are completed
• a series of one-off scripts for each command; they utilize objects in memory instantiated in the background process with startup()
• a completely different shell, like ipython; I'd like to integrate this with a standard shell, eg bash.

I am familiar with click , argparse , subprocess , etc., and as far as I can tell they accept a single command and block until completion. I specifically seek something that interacts with a background process so that expensive startup (loading objects into memory) is handled only once. I have looked at both python daemon and service packages, but I'm unsure if these are the right tool for the job also.

How can I accomplish this? I feel as though I don't know what to google to get the answer I need...

Answer 1

this is just one way you might do this... (there are other ways as well, this is just a pretty simple method)

you could use a server as your long running process (you would then turn it into a service using init systemV or upstart)

hardworker.py

import flask

app = flask.Flask("__main__")

@app.route("/command1")
def do_something():
    time.sleep(20)
    return json.dumps({"result":"OK"})

@app.route("/command2")
def do_something_else():
    time.sleep(26)
    return json.dumps({"result":"OK","reason":"Updated"})


if __name__ == "__main__":
   app.run(port=5000)

then your client could just make simple http requests against your "service"

thin_client.sh

if [[ $1 == "command1" ]]; then
   curl http://localhost:5000/command1
else if [[ $1 == "command2" ]]; then
   curl http://localhost:5000/command2
fi;