Run bunch of commands in parallel, with an option to specify the maximum number of commands to run at a time.

runner.py

import subprocess
import time

commands_to_run = ['ls -alh' for _ in range(100)]
max_procs = 16

processes = []
while (len(processes) > 0) or (len(commands_to_run) > 0):
    
    if (len(processes) < max_procs) & (len(commands_to_run) > 0):
        this_cmd = commands_to_run.pop()
        print(this_cmd)
        this_proc = subprocess.Popen(this_cmd, shell=True)
        processes.append(this_proc)
    
    for i in range(len(processes)):
        this_proc = processes[i]
        if this_proc.poll() is not None:
            return_code = this_proc.poll()
            print('Process exited with code: ' + str(return_code))
            del processes[i]
            break

    time.sleep(5)