Tested and working on Linux and Windows. I added OSX, I think it'll work. :)

task_manager_listing.py

import os, sys

"""
Author: https://github.com/angeloped
Do anything you want with this code.
"""

# determine operating system
os_type = sys.platform.lower()

# determine command to be executed
if "linux" in os_type:
	command="ps ax"
elif "windows" in os_type:
	command="tasklist"
elif "darwin" in os_type:
	command="ps ax"

# execute command via pipe
pipe_output = os.popen(command).read().split("\n")

# delete separators
if "windows" in os_type:
	del pipe_output[1]

# split whitespaces/tabs delimiters
processes = [pse.split() for pse in pipe_output if not pse == ""]

print(processes)