Python how to determine if a subprocess is already running?

Question

I'm able to create a subprocess.

process = subprocess.Popen(
    [
        r"C:\Program Files\BlueStacks_nxt\HD-Player.exe",
        "--instance",
        "Nougat32",
        "--cmd",
        "launchApp",
        "--package",
        "com.supercell.clashofclans",
    ],
    stderr=subprocess.PIPE,
)

However, I only want to create one if there isn't one that already exists. If there is one that exists, I want to focus on the window and not create a new process. Is there a way I can achieve this?