aviadpriel / tldextract

Accurately separates a URL’s subdomain, domain, and public suffix, using the Public Suffix List (PSL).

tldextract

tldextract accurately separates a URL's subdomain, domain, and public suffix, using the Public Suffix List (PSL).

Say you want just the "google" part of https://www.google.com. Everybody gets this wrong. Splitting on the "." and taking the 2nd-to-last element only works for simple domains, e.g. .com. Consider http://forums.bbc.co.uk: the naive splitting method will give you "co" as the domain, instead of "bbc". Rather than juggle TLDs, gTLDs, or ccTLDs yourself, tldextract extracts the currently living public suffixes according to the Public Suffix List.

A "public suffix" is one under which Internet users can directly register names.

A public suffix is also sometimes called an effective TLD (eTLD).

Usage

>>> import tldextract

>>> tldextract.extract('http://forums.news.cnn.com/')
ExtractResult(subdomain='forums.news', domain='cnn', suffix='com')

>>> tldextract.extract('http://forums.bbc.co.uk/') # United Kingdom
ExtractResult(subdomain='forums', domain='bbc', suffix='co.uk')

>>> tldextract.extract('http://www.worldbank.org.kg/') # Kyrgyzstan
ExtractResult(subdomain='www', domain='worldbank', suffix='org.kg')

ExtractResult is a namedtuple, so it's simple to access the parts you want.

>>> ext = tldextract.extract('http://forums.bbc.co.uk')
>>> (ext.subdomain, ext.domain, ext.suffix)
('forums', 'bbc', 'co.uk')
>>> # rejoin subdomain and domain
>>> '.'.join(ext[:2])
'forums.bbc'
>>> # a common alias
>>> ext.registered_domain
'bbc.co.uk'

Note subdomain and suffix are optional. Not all URL-like inputs have a subdomain or a valid suffix.

>>> tldextract.extract('google.com')
ExtractResult(subdomain='', domain='google', suffix='com')

>>> tldextract.extract('google.notavalidsuffix')
ExtractResult(subdomain='google', domain='notavalidsuffix', suffix='')

>>> tldextract.extract('http://127.0.0.1:8080/deployed/')
ExtractResult(subdomain='', domain='127.0.0.1', suffix='')

If you want to rejoin the whole namedtuple, regardless of whether a subdomain or suffix were found:

>>> ext = tldextract.extract('http://127.0.0.1:8080/deployed/')
>>> # this has unwanted dots
>>> '.'.join(ext)
'.127.0.0.1.'
>>> # join each part only if it's truthy
>>> '.'.join(part for part in ext if part)
'127.0.0.1'

By default, this package supports the public ICANN TLDs and their exceptions. You can optionally support the Public Suffix List's private domains as well.

This package started by implementing the chosen answer from this StackOverflow question on getting the "domain name" from a URL. However, the proposed regex solution doesn't address many country codes like com.au, or the exceptions to country codes like the registered domain parliament.uk. The Public Suffix List does, and so does this package.

Install

Latest release on PyPI:

pip install tldextract

Or the latest dev version:

pip install -e 'git://github.com/john-kurkowski/tldextract.git#egg=tldextract'

Command-line usage, splits the url components by space:

tldextract http://forums.bbc.co.uk
# forums bbc co.uk

Note about caching

Beware when first calling tldextract, it updates its TLD list with a live HTTP request. This updated TLD set is usually cached indefinitely in $HOME/.cache/python-tldextract. To control the cache's location, set TLDEXTRACT_CACHE environment variable or set the cache_dir path in TLDExtract initialization.

(Arguably runtime bootstrapping like that shouldn't be the default behavior, like for production systems. But I want you to have the latest TLDs, especially when I haven't kept this code up to date.)

# extract callable that falls back to the included TLD snapshot, no live HTTP fetching
no_fetch_extract = tldextract.TLDExtract(suffix_list_urls=None)
no_fetch_extract('http://www.google.com')

# extract callable that reads/writes the updated TLD set to a different path
custom_cache_extract = tldextract.TLDExtract(cache_dir='/path/to/your/cache/')
custom_cache_extract('http://www.google.com')

# extract callable that doesn't use caching
no_cache_extract = tldextract.TLDExtract(cache_dir=None)
no_cache_extract('http://www.google.com')

If you want to stay fresh with the TLD definitions--though they don't change often--delete the cache file occasionally, or run

tldextract --update

or:

env TLDEXTRACT_CACHE="~/tldextract.cache" tldextract --update

It is also recommended to delete the file after upgrading this lib.

Advanced usage

Public vs. private domains

The PSL maintains a concept of "private" domains.

PRIVATE domains are amendments submitted by the domain holder, as an expression of how they operate their domain security policy. … While some applications, such as browsers when considering cookie-setting, treat all entries the same, other applications may wish to treat ICANN domains and PRIVATE domains differently.

By default, tldextract treats public and private domains the same.

>>> extract = tldextract.TLDExtract()
>>> extract('waiterrant.blogspot.com')
ExtractResult(subdomain='waiterrant', domain='blogspot', suffix='com')

The following overrides this.

>>> extract = tldextract.TLDExtract()
>>> extract('waiterrant.blogspot.com', include_psl_private_domains=True)
ExtractResult(subdomain='', domain='waiterrant', suffix='blogspot.com')

or to change the default for all extract calls,

>>> extract = tldextract.TLDExtract( include_psl_private_domains=True)
>>> extract('waiterrant.blogspot.com')
ExtractResult(subdomain='', domain='waiterrant', suffix='blogspot.com')

The thinking behind the default is, it's the more common case when people mentally parse a URL. It doesn't assume familiarity with the PSL nor that the PSL makes such a distinction. Note this may run counter to the default parsing behavior of other, PSL-based libraries.

Specifying your own URL or file for Public Suffix List data

You can specify your own input data in place of the default Mozilla Public Suffix List:

extract = tldextract.TLDExtract(
    suffix_list_urls=["http://foo.bar.baz"],
    # Recommended: Specify your own cache file, to minimize ambiguities about where
    # tldextract is getting its data, or cached data, from.
    cache_dir='/path/to/your/cache/',
    fallback_to_snapshot=False)

The above snippet will fetch from the URL you specified, upon first need to download the suffix list (i.e. if the cached version doesn't exist).

If you want to use input data from your local filesystem, just use the file:// protocol:

extract = tldextract.TLDExtract(
    suffix_list_urls=["file://absolute/path/to/your/local/suffix/list/file"],
    cache_dir='/path/to/your/cache/',
    fallback_to_snapshot=False)

Use an absolute path when specifying the suffix_list_urls keyword argument. os.path is your friend.

The command line update command can be used with a url or local file you specify:

tldextract --update --suffix_list_url "http://foo.bar.baz"

This could be useful in production when you don't want the delay associated with updating the suffix list on first use, or if you are behind a complex firewall that prevents a simple update from working.

FAQ

Can you add suffix ____? Can you make an exception for domain ____?

This project doesn't contain an actual list of public suffixes. That comes from the Public Suffix List (PSL). Submit amendments there.

(In the meantime, you can tell tldextract about your exception by either forking the PSL and using your fork in the suffix_list_urls param, or adding your suffix piecemeal with the extra_suffixes param.)

If I pass an invalid URL, I still get a result, no error. What gives?

To keep tldextract light in LoC & overhead, and because there are plenty of URL validators out there, this library is very lenient with input. If valid URLs are important to you, validate them before calling tldextract.

This lenient stance lowers the learning curve of using the library, at the cost of desensitizing users to the nuances of URLs. Who knows how much. But in the future, I would consider an overhaul. For example, users could opt into validation, either receiving exceptions or error metadata on results.

Contribute

Setting up

1. git clone this repository.
2. Change into the new directory.
3. pip install tox

Running the test suite

Run all tests against all supported Python versions:

tox --parallel

Run all tests against a specific Python environment configuration:

tox -l
tox -e py37