Regex to detect one of several strings

Question

I\'ve got a list of email addresses belonging to several domains. I\'d like a regex that will match addresses belonging to three specific domains (for this example: foo, bar

Answer 1

You don't need a regex to find whether a string contains at least one of a given list of substrings. In Python:

def contain(string_, substrings):
    return any(s in string_ for s in substrings)

The above is slow for a large string_ and many substrings. GNU fgrep can efficiently search for multiple patterns at the same time.

Using regex

import re

def contain(string_, substrings):
    regex = '|'.join("(?:%s)" % re.escape(s) for s in substrings)
    return re.search(regex, string_) is not None

Related

• Multiple Skip Multiple Pattern Matching Algorithm (MSMPMA) [pdf]