login validation

check_login.py

import re
import random
import time


def make_check_login_regexes():
    line_start= r"""^([a-zA-Z])"""
    long_line_expr = re.compile(line_start + r"""
              ([A-Za-z0-9\.-]{0,18})  # латинские буквы, цифры, точки и минус 
              ([a-zA-Z0-9])           # alphanumeric 
              $""", re.VERBOSE)
    one_letter_line_exr = line_start + r"$"

    return re.compile(one_letter_line_exr), re.compile(long_line_expr)


ONE_CHAR_REGEX, MULTI_CHAR_REGEX = make_check_login_regexes()


def check_login_string_with_regex(login):
    
    string_length = len(login)

    result = False

    if string_length == 0:
        result = False

    elif string_length > 20:
        result = False

    elif string_length == 1:
      result = ONE_CHAR_REGEX.match(login) is not None
    else:
      result = MULTI_CHAR_REGEX.match(login) is not None
    return result


def is_ascii(s):
   return all(ord(c) < 128 for c in s)


def check_login_string(login):

    string_length = len(login)

    result = is_ascii(login)

    if string_length == 0:
        result = False

    elif string_length > 20:
        result = False

    elif string_length == 1:
      result = login.isalpha()

    else:
      result = login[0].isalpha() 
      result = result and login[-1].isalnum()
      if len(login) > 2:
          result = result and all(map(lambda ch: ch.isalnum() or ch in '.-', login[1:-1]))

    return result
      
      
def gen_rand_login():
  lenght = random.randint(1, 30)
  return ''.join(chr(random.randint(1, 130)) for x in range(lenght))


def bench_validator(validator, array):
  
  start = time.monotonic()

  for f in array:
    validator(f)

  end = time.monotonic()

  print('{0} time = {1}'.format(str(validator), end - start))

if __name__ == '__main__':
    logins = [gen_rand_login() for l in range(1 << 20)]

    bench_validator(check_login_string_with_regex, logins)
    bench_validator(check_login_string, logins)