Handy OUI lookup script for Python 3+. Tested on Windows 10.

oui3.py

#!/usr/bin/python

# Who owns the OUI? IEEE knows.
#
# Auto-refreshes once a month.
# Run with -u to force update.

from urllib.request import urlopen
from getpass import getuser
import codecs
import sys
import time
import os
import re

USER_HOME = "~"
OUI_FILE_STORE = os.path.join(os.path.expanduser(USER_HOME), ".oui-cache")
CACHE_TIME = 2592000  # 30 days should be fine
IEEE_URL = "http://standards.ieee.org/develop/regauth/oui/oui.txt"


def clean_input(user_input):
    # """
    # Strip colons
    # """
    return "".join(user_input.split('-')[:3])


def update_cache():
    # """
    # Update our local file from the IEEE OUI
    # list
    # """
    print(">>> Updating Cache")
	try:
		with open(OUI_FILE_STORE, 'r') as outfile:
			for lne in urlopen(IEEE_URL).readlines():
				outfile.write(lne)
	except FileNotFoundError:
		with open(OUI_FILE_STORE, 'wb') as outfile:
			for lne in urlopen(IEEE_URL).readlines():
				outfile.write(lne)
    print(">>> Done")


def process_args():
    # """
    # Parse our args
    # """
    if sys.argv[1] == "-u":
        update_cache()
        if len(sys.argv) > 2:
            user_input = sys.argv[2]
        else:
            sys.exit(0)
    else:
        user_input = sys.argv[1]

    return clean_input(user_input)


def get_manufacturer(raw_mac):
    # """
    # Return manufacturer from cached file
    # """
    clean_mac = clean_input(raw_mac)
    try:
        if time.time() - os.stat(OUI_FILE_STORE).st_ctime > CACHE_TIME:
            update_cache()

    except OSError as err:
        if err.errno == 2:
            update_cache()

    with codecs.open(OUI_FILE_STORE,'r',encoding='utf8') as oui_list:
        for line in iter(oui_list):
            if re.search(clean_mac, line, re.IGNORECASE):
                return line.split("\t")[-1].strip()
    return "unknown"


if __name__ == "__main__":
    print(get_manufacturer(process_args()))

Hi, thank you for this, I have adapted it and use it. I found the following changes were needed for me with Python 3.10. Thought I'd share in case you'd like to reconsider your code (I am new to code, so feel free to tell me I am wrong).

Line 36 "with open(OUI_FILE_STORE, 'r') as outfile:" - needed 'wb' instead of 'r' to avoid an error - "argument must be str, not bytes"

Line 68 "if time.time() - os.stat(OUI_FILE_STORE).st_ctime > CACHE_TIME:" - changed ctime to mtime. For me, without this it didn't detect the last updated date of the local file correctly, and tried to update the file on every mac address that it ran, in my case, I pushing a heap of MACs from a different script, which meant it updated the oui file everytime a MAC came to it.