Django model default=datetime.datetime.now() & get_or_create 一个BUG?!

# -*- coding: UTF-8 -*-

import datetime

from django.db import models

class Demo(models.Model):

    class Meta:

        db_table = 't_demo'

    unique_char = models.CharField()

    create_time = models.DateTimeField(default = datetime.datetime.now())

#!/usr/bin/env python

# -*- coding: utf-8 -*-

import os

os.environ["DJANGO_SETTINGS_MODULE"] = "test.settings"

import time, datetime

from test import Demo

if __name__ == "__main__":

    while True:

        demo, created = Demo.objects.get_or_create(unique_char = datetime.datetime.now().strftime('%Y-%m-%d %H:%M:%S'))

        time.sleep(1)