Easy way python async method wanted

Question

I am developing a small media player app on raspberry pi. So This have two main functions. Namely radio and file player. If entered into file player below is the code :

        
        process = subprocess.Popen(['omxplayer',songs[0],'-o','local'],  stdout=subprocess.PIPE )
        #stdout = process.communicate()[0]
        
        nxt=0
        while True:
            print("looping")
            output = process.stdout.readline()
            if nxt>1:     
                process = subprocess.Popen(['omxplayer', songs[nxt],'-o','local'], stdout=subprocess.PIPE)
                output = process.stdout.readline()
                #stdout = process.communicate()[0]
                
            if output =='' :
                print("2")
            if output:
                print("finshed")
                nxt=nxt+1
            if GPIO.input(7)==0:
                break

The problem is code after and outside this loop doesnt work before the subprocess is finished. How can I use ayncio so that some gpio readings can be taken and exit this loop once needed ? I really spent 8 hours to figureout this googling this. But all available tutorials are very difficult to understand.

Answer 1

If you're interacting with a live process, you need to have some handle to do so - often this will look like a socket, which seems to be what the process expects from these examples (briefly skimmed)

• https://www.raspberrypi.org/forums/viewtopic.php?t=28614
• https://github.com/stifi/Python-omxplayer-Socket

However, in order for your Python process to also do some logic while managing this, you'll need one of the following

• threading: likely easier to reason about, but with more troublesome caveats (limited maximum interactions, cleanup, serializing commands..)
• asyncio: likely the best choice overall, but potentially more troublesome to reason about at first
• multiprocessing: similar to threading, but perhaps the most troublesome to reason about (ie. how do the processes communicate?) and least beneficial for your case (simply writing or reading a socket)

---

It's beyond the scope of the question, but to get started, you may find it easy to

• write a small test script for interacting with sockets to learn how they work
• play with with a good, but simple async web framework like Tornado to understand how asynchronous logic behaves
• combine 'em using with Tornado's IOStream logic to make a complete example
• continue with your new design ideas