Username and Email address generation script

FHCC-username-generator.py

#!/usr/bin/env python3
"""
Account naming rules

Rule 1: firstname + lastname is less 18 or less characters long total
        == firstname + "." + lastname  (john.doe)
        if conflict append an integer (starting with 2) to the end of the username
        === firstname + "." + lastname + int (john.doe2)

Rule 2: firstname + lastname is greater than 18 characters long total *and* 
        firstname_initial + lastname <= 18 characters long total
        == firstname_initial + "." + lastname (jimmy reallylongname = j.reallylongname)
        if conflict append an integer (starting with 2) to the end of the username
        == firstname_initial + "." + lastname (johnny reallylongname = j.reallylongname2)

Rule 3: firstname + lastname is greater than 18 characters long total *and* 
        firstname_initial + lastname > 18 characters long total
        == firstname_initial + "." + lastname[truncated to 17 chars] (jimmy reallyverylongname =  j.reallyverylongnam)
        if conflict append an integer (starting with 2) to the end of the username
        == firstname_initial + "." + lastname[truncated to 17 chars] (jimbo reallyverylongname =  j.reallyverylongnam2)
"""
import sys


def generate(first_name, last_name, email_domain):
    """
    Take a first name, last name and based on the defined rules print the new users
    unique username and email address. 
    """
    first_name = first_name.replace(" ", "").lower()
    last_name = last_name.replace(" ", "").lower()
    email_domain = email_domain.lower()
    if len(first_name + last_name) <= 18:
        username = dupe_fix("{}.{}".format(first_name, last_name))
        print("sAMAccountName: {}".format(username))
        print("Email Address:  {}@{}".format(username, email_domain))
    elif len(first_name[0] + last_name) <=18: 
        username = dupe_fix("{}.{}".format(first_name[0], last_name))
        print("sAMAccountName: {}".format(username))
        print("Email Address:  {}@{}".format(username, email_domain))
    else:
        username = dupe_fix("{}.{}".format(first_name[0], last_name[:17]))
        print("sAMAccountName: {}".format(username))
        print("Email Address:  {}@{}".format(username, email_domain))

def dupe_fix(username):
    """
    Check to see if the generanted username is an exising username and if so generate
    a non conflicting username by appeneding an integer until if finds a unique username.
    """
    conflict = 0
    while True:
        if username not in existing_usernames:
            break
        conflict += 1
        if username[-1].isdigit():
            username = "{}{}".format(username[:-1], conflict + 1)
        else:
            username = "{}{}".format(username, conflict + 1)
    return(username)


#This is just to demo username collision detection, in production you'd need to retrive
#your alias/username list externally from this script
existing_usernames = ['john.doe',
                      'jane.doe',
                      'robert.mcdermott',
                      'robert.mcdermott2',
                      'c.trakarnsilpa',
                      'j.reallylongname',
                      'j.reallylongerlastn']
  

if __name__ == "__main__":
    if len(sys.argv) < 3:
        print("Usage: {} firstname lastname".format(sys.argv[0]))
        sys.exit(1)
        
    email_domain = "fredhutch.org"
    first_name = sys.argv[1]
    last_name = sys.argv[2]
    generate(first_name, last_name, email_domain)