How to extract top-level domain name (TLD) from URL

user_105066 0
Viewed 81358

how would you extract the domain name from a URL, excluding any subdomains?

My initial simplistic attempt was:

'.'.join(urlparse.urlparse(url).netloc.split('.')[-2:])

This works for http://www.foo.com, but not http://www.foo.com.au. Is there a way to do this properly without using special knowledge about valid TLDs (Top Level Domains) or country codes (because they change).

thanks

dns extract url parsing python
8 Answers

No, there is no "intrinsic" way of knowing that (e.g.) zap.co.it is a subdomain (because Italy's registrar DOES sell domains such as co.it) while zap.co.uk isn't (because the UK's registrar DOESN'T sell domains such as co.uk, but only like zap.co.uk).

You'll just have to use an auxiliary table (or online source) to tell you which TLD's behave peculiarly like UK's and Australia's -- there's no way of divining that from just staring at the string without such extra semantic knowledge (of course it can change eventually, but if you can find a good online source that source will also change accordingly, one hopes!-).

user_958100

Using this file of effective tlds which someone else found on Mozilla's website:

from __future__ import with_statement
from urlparse import urlparse

# load tlds, ignore comments and empty lines:
with open("effective_tld_names.dat.txt") as tld_file:
    tlds = [line.strip() for line in tld_file if line[0] not in "/\n"]

def get_domain(url, tlds):
    url_elements = urlparse(url)[1].split('.')
    # url_elements = ["abcde","co","uk"]

    for i in range(-len(url_elements), 0):
        last_i_elements = url_elements[i:]
        #    i=-3: ["abcde","co","uk"]
        #    i=-2: ["co","uk"]
        #    i=-1: ["uk"] etc

        candidate = ".".join(last_i_elements) # abcde.co.uk, co.uk, uk
        wildcard_candidate = ".".join(["*"] + last_i_elements[1:]) # *.co.uk, *.uk, *
        exception_candidate = "!" + candidate

        # match tlds: 
        if (exception_candidate in tlds):
            return ".".join(url_elements[i:]) 
        if (candidate in tlds or wildcard_candidate in tlds):
            return ".".join(url_elements[i-1:])
            # returns "abcde.co.uk"

    raise ValueError("Domain not in global list of TLDs")

print get_domain("http://abcde.co.uk", tlds)

results in:

abcde.co.uk

I'd appreciate it if someone let me know which bits of the above could be rewritten in a more pythonic way. For example, there must be a better way of iterating over the last_i_elements list, but I couldn't think of one. I also don't know if ValueError is the best thing to raise. Comments?

user_1251850
SLott_106610

In Python I used to use tldextract until it failed with a url like www.mybrand.sa.com parsing it as subdomain='order.mybrand', domain='sa', suffix='com'!!

So finally, I decided to write this method

IMPORTANT NOTE: this only works with urls that have a subdomain in them. This isn't meant to replace more advanced libraries like tldextract

def urlextract(url):
  url_split=url.split(".")
  if len(url_split) <= 2:
      raise Exception("Full url required with subdomain:",url)
  return {'subdomain': url_split[0], 'domain': url_split[1], 'suffix': ".".join(url_split[2:])}
user_804340
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