Help with Regex for domain names

[MRAB]

Feyo wrote:
> I'm trying to figure out how to write efficiently write a regex for
> domain names with a particular top level domain. Let's say, I want to
> grab all domain names with country codes .us, .au, and .de.
> 
> I could create three different regexs that would work:
> regex = re.compile(r'[\w\-\.]+\.us)
> regex = re.compile(r'[\w\-\.]+\.au)
> regex = re.compile(r'[\w\-\.]+\.de)
> 
> How would I write one to accommodate all three, or, better yet, to
> accommodate a list of them that I can pass into a method call? Thanks!
 >
regex = re.compile(r'[\w\-\.]+\.(?:us|au|de)')

If you have a list of country codes ["us", "au", "de"] then you can
build the regular expression from it:

regex = re.compile(r'[\w\-\.]+\.(?:%s)' % '|'.join(domains))