django模型递归导入-如何解决

Question

我有一个模特project_phase

    from django.db import models
    from django.utils import simplejson
    from core.models import pmo_review_task

它引用pmo_review_task (因为它在保存ovewrite中创建了一个pmo_review_task )

from django.db import models
from datetime import datetime
from django.contrib.auth.models import User
from core.models import sc_review_task

它引用引用project_phase的project_phase (因为它在保存的project_phase中创建了一个project_phase)

from django.db import models
from core.models import project_phase

因此，它以project_phase导入、pmo_review_task导入、sc_review_task导入、project_phase结束，我猜它以某种方式产生了这个错误：

Unhandled exception in thread started by <bound method Command.inner_run of <django.core.management.commands.runserver.Command object at 0x010ACFB0>>
Traceback (most recent call last):
  File "C:\Python27\lib\site-packages\django\core\management\commands\runserver.py", line 88, in inner_run
    self.validate(display_num_errors=True)
  File "C:\Python27\lib\site-packages\django\core\management\base.py", line 249, in validate
    num_errors = get_validation_errors(s, app)
  File "C:\Python27\lib\site-packages\django\core\management\validation.py", line 35, in get_validation_errors
    for (app_name, error) in get_app_errors().items():
  File "C:\Python27\lib\site-packages\django\db\models\loading.py", line 146, in get_app_errors
    self._populate()
  File "C:\Python27\lib\site-packages\django\db\models\loading.py", line 64, in _populate
    self.load_app(app_name)
  File "C:\Python27\lib\site-packages\django\db\models\loading.py", line 78, in load_app
    models = import_module('.models', app_name)
  File "C:\Python27\lib\site-packages\django\utils\importlib.py", line 35, in import_module
    __import__(name)
  File "C:\work\Portman\core\models\__init__.py", line 4, in <module>
    from pmo_review_task import pmo_review_task
  File "C:\work\Portman\core\models\pmo_review_task.py", line 5, in <module>
    from core.models import sc_review_task
  File "C:\work\Portman\core\models\sc_review_task.py", line 3, in <module>
    from core.models import project_phase
  File "C:\work\Portman\core\models\project_phase.py", line 4, in <module>
    from core.models import pmo_review_task
ImportError: cannot import name pmo_review_task

我该如何克服这一切？

Answer 1

有两种方式：

1. 在方法中导入模型(如@YujiTomita建议的那样).
2. 从django.db.models中使用get_model函数，该函数是为惰性模型导入而设计的.：

'project_phase') = project_phase =get_model(“核心”)

我更喜欢第二种方法，但两种方法都可以。

Answer 2

在project_phase方法中导入save。

只要代码被执行，导入就会被调用。

如果它位于全局模块命名空间中(在顶部)，那么它将立即被调用，您将遇到您所描述的循环导入问题，因为一个文件导入另一个文件，该文件导入原始文件。

如果将问题导入语句放入函数中，则在导入文件时调用它。

import foo # executed upon importing this file. 

def import_foo_when_called():
    import foo # only executed when function is called, thus no problems when 
               # another module imports this file.

Answer 3

Django 1.9及以上

因为get_model()在django.db.models中已经在1.9中被删除。

使用django.apps.get_model()

类似问题：What is the equivalent of django.db.models.loading.get_model() in Django 1.9?

或者在引号中使用应用标签，如果您只是使用它来创建foreignkey。

而不是from core.models import project_phase

models.ForeignKey("core.project_phase")