A python code that describes how regex can be used to validate an email ID

validate_email.py

import re
test_email_1 = "Jane.doe1971@gmail.com"
test_email_2 = "JD@msn.org.edu"
test_email_3 = "J.A.N.E@web123.AI"
test_emails = [test_email_1, test_email_2, test_email_3]

def extract_info(email_string):
    # Search for username
    # Methodology
    # All alphabets and numbers before @
    # () anything between parenthesis is matched and returned
    # [] contains the set of characters 
    #  that may occur in the matched string
    u = re.search('([A-Za-z0-9\.]*)@', email_string)
    username = u.group(1)

    # Search for domain name
    # All alphabets and numbers between @ and dot
    # Escape the dot using backslash
    d = re.search('@([A-Za-z0-9]*)\.', email_string)
    domain = d.group(1)

    # Search for TLD
    # Anything after the first dot 
    #  that occurs after the @ sign
    t = re.search('@[A-Za-z0-9]*\.([A-Za-z\.]*)', email_string)
    TLD = t.group(1)

    print("\n*****************************\nEMAIL: ", email_string)
    print("Username: ", username)
    print("Domain: ", domain)
    print("TLD: ", TLD, "\n")

for email in test_emails:
    extract_info(email)