Django模型 - 问题导入

Question

我已经将我的模型文件重构为一个模块 - 这样就可以更容易地维护代码,因为它已经增长了很多.

有趣的是,它不适用于引用另一个引用其中第一个类的类中的一个类:

UPD:循环引用令人困惑的python,这就是问题所引起的.当您仅从模型定义中引用其他模型时,这很容易修复.但是,Picture具有引用paperType类的方法,反之亦然 - 如何修复它？

这是班级图片:

from django.db import models
from django.utils import simplejson
from picviewer.models import Collection, ImageSizeRatio, printSize

class Picture(models.Model):
    name = models.TextField(null=False,blank=False,unique=False)
    collection = models.ForeignKey(Collection)
    popularity = models.IntegerField(default=0,unique=False)
    isPurchasable = models.BooleanField(default=False)
    allowBuyExclusive = models.BooleanField(default=False)
    basePrice = models.DecimalField(decimal_places=2,max_digits=8)
    imageSizeRatio = models.ForeignKey(ImageSizeRatio)
    imageThumbnail = models.FileField(upload_to='pictures')
    imagePreview = models.FileField(upload_to='pictures')
    imageSmall = models.FileField(upload_to='pictures')
    imageNormal = models.FileField(upload_to='pictures')
    imageLarge = models.FileField(upload_to='pictures')
    imageHuge = models.FileField(upload_to='pictures')
    allowedPrintSize = models.ManyToManyField(printSize)

这是它引用的printSize类 - 你看它调用Picture函数来对指定printSize的图片做一些数学运算:

from django.db import models
from picviewer.models import paperType
from picviewer.models import Picture

class printSize (models.Model):
    name = models.CharField(null=False,blank=False,unique=True,max_length=60)
    width = models.IntegerField(null=False,blank=False)
    height = models.IntegerField(null=False,blank=False)
    allowedPaperType = models.ManyToManyField(paperType)
    #isActive = models.NullBooleanField(null=True, default=None)

    def json(self, picture_id, base_price):
        sizes_selector = printSize.objects.filter(picture__id = picture_id)
        sizes = list()
        for size in sizes_selector:
            papers = list()
            for paper in size.allowedPaperType.all():
                cost_for_paper = Picture.objects.get(id=picture_id).calculatePrice(paper.id,size.id)
                p = dict(id = paper.id,
                         name = paper.name,
                         description = paper.description,
                         price = paper.pricePerSqMeter.__str__(),
                         cost = "%.2f" % cost_for_paper)
                papers.append(p)
            s = dict(id = size.id,
                     name = size.name,
                     width = size.width,
                     height = size.height,
                     allowedPapers = papers)
            sizes.append(s)
        return sizes

现在这是我在shell中尝试导入图片:

>>> from picviewer.models import Picture
Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "D:\~Sasha\eclipse_workspace\zavalen\picviewer\models\Picture.py", line 4, in <module>
    from picviewer.models import Collection, ImageSizeRatio, printSize
  File "D:\~Sasha\eclipse_workspace\zavalen\picviewer\models\printSize.py", line 4, in <module>
    from picviewer.models import Picture
ImportError: cannot import name Picture
>>>

我能治好吗？:)

Answer 1

要避免循环导入,请将FK模型指定为字符串,例如

collection = models.ForeignKey('Collection') # Collection is in the same module

要么

collection = models.ForeignKey('myapp.Collection') # Collection is in another app