[SOLVED] How do I pass a list of strings to an external command in Python?

How do I pass a list of strings to an external command in Python?

I am writing a Python program that will download a list of bad IP addresses and add/remove those from a table in OpenBSD pf. The program downloads the list, formats them (as IP address objects), and passes them to the pfctl command. Right now I have it working as a loop that calls pfctl once for each string thusly:

for item in addedlist:
    subprocess.run(['pfctl', '-t', const.PF_LISTNAME, '-T', 'add',\
    str(item)], check=True, stderr=subprocess.DEVNULL)

for item in deletedlist:
    subprocess.run(['pfctl', '-t', const.PF_LISTNAME, '-T', 'delete',\
    str(item)], check=True, stderr=subprocess.DEVNULL)

where:

addedlist and deletedlist are the formatted lists of IP address objects to be added and removed, respectively.

I would like to run the pfctl command only once for each list and pass addedlist and deletedlist to the command in one shot since the lists (coughIPv6*cough*) can be quite lengthy. When I try to do it, though, Python complains about not expecting a list.

Any help would be appreciated.

Solution

You'll have to concatenate the items to the argument list, not nest the items lists in it.

We'll also use a list comprehension to call str on the items.

subprocess.run(
    ["pfctl", "-t", const.PF_LISTNAME, "-T", "add"]
    + [str(item) for item in addedlist],
    check=True,
    stderr=subprocess.DEVNULL,
)
subprocess.run(
    ["pfctl", "-t", const.PF_LISTNAME, "-T", "delete"]
    + [str(item) for item in deletedlist],
    check=True,
    stderr=subprocess.DEVNULL,
)