在python文件中操作django orm提示环境变量设置问题

今天在通过python文件中单独操作并运行django orm操作的时候，运行.py文件时遇到以下的问题：

Traceback (most recent call last):
...
    self.db_tablespace = db_tablespace or settings.DEFAULT_INDEX_TABLESPACE
  File "D:ProgramPython37libsite-packagesdjangoconf\__init__.py", line 56, in __getattr__
    self._setup(name)
  File "D:ProgramPython37libsite-packagesdjangoconf\__init__.py", line 39, in _setup
    % (desc, ENVIRONMENT_VARIABLE))
django.core.exceptions.ImproperlyConfigured: Requested setting DEFAULT_INDEX_TABLESPACE, but settings are not configured. You must either define the environment variable DJANGO_SETTINGS_MODULE or call settings.configure() before accessing settings.

查看.py文件的代码如下，简单的几行，看起来也没什么问题：

import os
import django
from orm_practice import models

os.environ.setdefault("DJANGO_SETTINGS_MODULE", "BookManage.settings")
django.setup()

ret = models.Person.objects.all()
print(ret)

经过对比老师课上写的代码，发现from orm_practice import models 这一行不能放在环境变量设置之前，按以下修改的代码就可以正常运行：

import os
import django

os.environ.setdefault("DJANGO_SETTINGS_MODULE", "BookManage.settings")
django.setup()

from orm_practice import models
ret = models.Person.objects.all()
print(ret)

再运行的话就不再报错了。

<QuerySet []>

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