我理解如何分解模型，并且我理解为什么循环模块依赖关系会把事情搞砸，但是我遇到了一个问题，将模型分解成单独的文件似乎会导致循环依赖。下面是代码的一个摘录，我将用失败过程的回溯来跟踪它:
elearning/tasks.py
from celery.task import task
@task
def decompress(pk):
from elearning.models import Elearning
Elearning.objects.get(pk=pk).decompress()
elearning/models.py
from competency.models import CompetencyProduct
from core.helpers import ugc_elearning
from elearning.fields import ArchiveFileField
class Elearning(CompetencyProduct):
archive = ArchiveFileField(upload_to=ugc_elearning)
def decompress(self):
import zipfile
src = self.archive.path
dst = src.replace(".zip","")
print "Decompressing %s to %s" % (src, dst)
zipfile.ZipFile(src).extractall(dst)
ecom/models/products.py
from django.db import models
from django.utils.translation import ugettext_lazy as _
from core.models import Slugable, Unique
from django_factory.models import Factory
from core.helpers import ugc_photos
class Product(Slugable, Unique, Factory):
photo = models.ImageField(upload_to=ugc_photos, width_field="photo_width", height_field="photo_height", blank=True)
photo_width = models.PositiveIntegerField(blank=True, null=True, default=0)
photo_height = models.PositiveIntegerField(blank=True, null=True, default=0)
description = models.TextField()
price = models.DecimalField(max_digits=16, decimal_places=2)
created = models.DateTimeField(auto_now_add=True)
modified = models.DateTimeField(auto_now=True)
ecom/models/__init__.py
from django.contrib.auth.models import User
from django.db import models
from ecom.models.products import Product, Credit, Subscription
from ecom.models.permissions import Permission
from ecom.models.transactions import Transaction, DebitTransaction, CreditTransaction, AwardTransaction, FinancialTransaction, PermissionTransaction, BundleTransaction
competency/models.py
from django.db import models
from django.utils.translation import ugettext_lazy as _
from core.models import Slugable, Unique
from ecom.models import Product
from rating.models import Rated
from trainer.models import Trainer
class Competency(Slugable, Unique):
class Meta:
verbose_name = _("Competency")
verbose_name_plural = _("Competencies")
description = models.TextField()
class CompetencyProduct(Product, Rated):
class Meta:
verbose_name = _("Product")
verbose_name_plural = _("Products")
release = models.DateField(auto_now_add=True)
trainers = models.ManyToManyField(Trainer)
competencies = models.ManyToManyField(Competency, related_name="provided_by")
requirements = models.ManyToManyField(Competency, related_name="required_for", blank=True, null=True)
forsale = models.BooleanField("For Sale", default=True)
ecom/models/permissions.py
from django.contrib.auth.models import User
from django.db import models
from django.utils.translation import ugettext_lazy as _
from treebeard.mp_tree import MP_Node
from collective.models import Collective
from course.models import Course
from ecom.models.products import Product
class Permission(MP_Node):
class Meta:
app_label = "ecom"
product = models.ForeignKey(Product, related_name="permissions")
user = models.ForeignKey(User, related_name="permissions")
collective = models.ForeignKey(Collective, null=True)
course = models.ForeignKey(Course, null=True)
redistribute = models.BooleanField(default=False)
created = models.DateTimeField(auto_now_add=True)
modified = models.DateTimeField(auto_now=True)
accessed = models.DateTimeField(auto_now=True)
course/models.py
from django.db import models
from django.utils.translation import ugettext_lazy as _
from competency.models import CompetencyProduct
from ecom.models import Product
from rating.models import Rated
class Chapter(models.Model):
seq = models.PositiveIntegerField(name="Sequence", help_text="Chapter number")
name = models.CharField(max_length=128)
note = models.CharField(max_length=128)
class Course(Product, Rated):
level = models.PositiveIntegerField(choices=CompetencyProduct.LEVELS)
chapters = models.ManyToManyField(Chapter)
class Bundle(models.Model):
class Meta:
unique_together = (("product", "chapter"),)
product = models.ForeignKey(Product, related_name="bundles")
chapter = models.ForeignKey(Chapter, related_name="bundles")
amount = models.PositiveIntegerField()
seq = models.PositiveIntegerField(name="Sequence", default=1)
从我所看到的，这里没有显式的循环递归，除了__init__.py中所需的引用，这似乎是在我的代码中发生的事情。下面是回溯:
File "/path/to/project/virtualenv/lib/python2.6/site-packages/celery/execute/trace.py", line 47, in trace
return cls(states.SUCCESS, retval=fun(*args, **kwargs))
File "/path/to/project/virtualenv/lib/python2.6/site-packages/celery/app/task/__init__.py", line 247, in __call__
return self.run(*args, **kwargs)
File "/path/to/project/virtualenv/lib/python2.6/site-packages/celery/app/__init__.py", line 175, in run
return fun(*args, **kwargs)
File "/path/to/project/django/myproj/elearning/tasks.py", line 5, in decompress
from elearning.models import Elearning
File "/path/to/project/django/myproj/elearning/models.py", line 2, in <module>
from competency.models import CompetencyProduct
File "/path/to/project/django/myproj/competency/models.py", line 5, in <module>
from ecom.models import Product
File "/path/to/project/django/myproj/ecom/models/__init__.py", line 5, in <module>
from ecom.models.permissions import Permission
File "/path/to/project/django/myproj/ecom/models/permissions.py", line 8, in <module>
from course.models import Course
File "/path/to/project/django/myproj/course/models.py", line 4, in <module>
from competency.models import CompetencyProduct
ImportError: cannot import name CompetencyProduct
我在这里要做的就是导入Elearning模型，它是CompetencyProduct的子类，然后是Product。然而，因为Product来自于更大的ecom/models.py的分解，ecom/__init__.py文件包含了所有分解模型的强制导入，包括Permission，它必须导入Course，而CompetencyProduct需要。
奇怪的是，整个网站运行完美。登录，购买，所有的一切。这个问题只发生在我试图在后台运行芹菜，并加载一个新任务，或者我试图使用Django环境运行shell脚本时。
我唯一的选择是从ecom应用程序中删除Permission，还是有更好，更智能的方法来处理这个问题?此外，如果您对我如何总体布局这个项目有任何意见，我将不胜感激。
您的问题是Permission导入Product，但两者都在ecom/models/__init__.py中导入。你应该找到一种方法，要么将这两个模型放在同一个文件中，要么将它们分开到两个应用程序中。