import random
import string
import time
import os


def create_reference_id(prefix="L"):
    """ create a unique identifier for human reference purpose
        shorter and more friendly than UUID
        not as secure as UUID

        >>> create_reference_id()
        'L-1498206382-HPJQXB'
    """
    return "{0}-{1}-{2}".format(
        prefix,
        int(time.time()) + os.getpid(),
        ''.join(random.sample(string.ascii_uppercase, 5))
    )