extract domain name from an URL likely string

extract_domain_name.py

import re

def extract_domain_name(url):
    """
    Given a URL string, returns the domain name without the TLD (top-level domain),
    or an empty string if the input is invalid.
    """
    if not isinstance(url, str):
        return ""
    url = url.strip().lower()
    pattern = r"(?:http[s]?://)?(?:www\.)?([^./]+)(?:\.[^./]+)*\.?(?:/[^/]*)?$"
    match = re.search(pattern, url)
    if not match:
        return ""
    return match.group(1)

test.py

from extract_domain_name import extract_domain_name
test_cases = ['http://www.example.com',
'http://www.example.cc/ad',
'www.example.net',
'www.example.net/ad',
'example.xyz/ad',
'example.com.cn',
'.example.org',
'.example.com/ad',
'example.',
'.example',
'.example.',
'example']
for test_case in test_cases:
    domain_name = extract_domain_name(test_case)
    print(f'{test_case}: {domain_name}')