【问题标题】：Connecting Models from different Apps - Django连接来自不同应用程序的模型 - Django
【发布时间】：2016-10-13 09:51:57
【问题描述】：

鉴于我有 4 个模型：

Project
User（来自 django.contrib.auth.models）
Sentence
Translation

我的 django 项目目录的结构如下：

 \myprojname
     \project
         models.py
     \data
         models.py

User 模型独立于 Projects 和 Sentences 模型，但它通过 ForeignKey 链接到 Projects 模型：

myprojname/projects/models.py 看起来像这样：

from django.db import models
from django.contrib.auth.models import User

class Project(models.Model):
    project_id = models.AutoField(primary_key=True)
    created_on = models.DateTimeField(auto_now_add=True)
    updated_on = models.DateTimeField(auto_now=True)

    name = models.CharField(max_length=140)
    # Admin user for the particular *Project* object.
    # Have the rights to write to the *Sentence* model.
    owner = models.ForeignKey(User)
    # Worker users that only have write access to the *Translation model.
    workers = models.ForeignKey(User, blank=True)

myprojname/data/models.py 看起来像这样：

from django.db import models
from django.contrib.auth.models import User

class Sentence(models.Model):
    text = models.TextField()
    translations = models.ManyToManyField('Translation', blank=True)

class Translation(models.Model):
    text = models.TextField()
    translator = models.ForeignKey(User)

现在Project 模型未连接到Sentence 模型。

我尝试将它与相对导入连接，即在myprojname/projects/models.py 中，我做到了：

from django.db import models
from django.contrib.auth.models import User
from ..data import Sentence

class Project(models.Model):
    # ...
    sentences = models.ForeignKey(Sentence)

但它在Python2.7 中返回了ValueError：

Traceback (most recent call last):
  File "/usr/local/lib/python2.7/dist-packages/django/utils/autoreload.py", line 226, in wrapper
    fn(*args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/commands/runserver.py", line 109, in inner_run
    autoreload.raise_last_exception()
  File "/usr/local/lib/python2.7/dist-packages/django/utils/autoreload.py", line 249, in raise_last_exception
    six.reraise(*_exception)
  File "/usr/local/lib/python2.7/dist-packages/django/utils/autoreload.py", line 226, in wrapper

    fn(*args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/django/__init__.py", line 18, in setup
    apps.populate(settings.INSTALLED_APPS)
  File "/usr/local/lib/python2.7/dist-packages/django/apps/registry.py", line 108, in populate
    app_config.import_models(all_models)
  File "/usr/local/lib/python2.7/dist-packages/django/apps/config.py", line 202, in import_models
    self.models_module = import_module(models_module_name)
  File "/usr/lib/python2.7/importlib/__init__.py", line 37, in import_module
    __import__(name)
  File "/home/alvas/data-project/myprojname/project/models.py", line 5, in <module>
    from ..data import Sentence
ValueError: Attempted relative import beyond toplevel package

在Python3 中，同样的错误：

Traceback (most recent call last):
  File "/home/alvas/.virtualenvs/payer/lib/python3.5/site-packages/django/utils/autoreload.py", line 226, in wrapper
    fn(*args, **kwargs)
  File "/home/alvas/.virtualenvs/payer/lib/python3.5/site-packages/django/core/management/commands/runserver.py", line 109, in inner_run
    autoreload.raise_last_exception()
  File "/home/alvas/.virtualenvs/payer/lib/python3.5/site-packages/django/utils/autoreload.py", line 249, in raise_last_exception
    six.reraise(*_exception)
  File "/home/alvas/.virtualenvs/payer/lib/python3.5/site-packages/django/utils/six.py", line 685, in reraise

    raise value.with_traceback(tb)
  File "/home/alvas/.virtualenvs/payer/lib/python3.5/site-packages/django/utils/autoreload.py", line 226, in wrapper
    fn(*args, **kwargs)
  File "/home/alvas/.virtualenvs/payer/lib/python3.5/site-packages/django/__init__.py", line 18, in setup
    apps.populate(settings.INSTALLED_APPS)
  File "/home/alvas/.virtualenvs/payer/lib/python3.5/site-packages/django/apps/registry.py", line 108, in populate
    app_config.import_models(all_models)
  File "/home/alvas/.virtualenvs/payer/lib/python3.5/site-packages/django/apps/config.py", line 202, in import_models
    self.models_module = import_module(models_module_name)
  File "/home/alvas/.virtualenvs/payer/lib/python3.5/importlib/__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 986, in _gcd_import
  File "<frozen importlib._bootstrap>", line 969, in _find_and_load
  File "<frozen importlib._bootstrap>", line 958, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 673, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 662, in exec_module
  File "<frozen importlib._bootstrap>", line 222, in _call_with_frames_removed
  File "/home/alvas/data-project/myprojname/project/models.py", line 5, in <module>
    from ..data import Sentence
ValueError: attempted relative import beyond top-level package

当我尝试在Python3 中进行非相对导入时：

from django.db import models
from django.contrib.auth.models import User
from myprojname.data import Sentence

class Project(models.Model):
    # ...
    sentences = models.ForeignKey(Sentence)

我明白了：

Traceback (most recent call last):
  File "/home/alvas/.virtualenvs/payer/lib/python3.5/site-packages/django/utils/autoreload.py", line 226, in wrapper
    fn(*args, **kwargs)
  File "/home/alvas/.virtualenvs/payer/lib/python3.5/site-packages/django/core/management/commands/runserver.py", line 109, in inner_run

    autoreload.raise_last_exception()
  File "/home/alvas/.virtualenvs/payer/lib/python3.5/site-packages/django/utils/autoreload.py", line 249, in raise_last_exception
    six.reraise(*_exception)
  File "/home/alvas/.virtualenvs/payer/lib/python3.5/site-packages/django/utils/six.py", line 685, in reraise
    raise value.with_traceback(tb)
  File "/home/alvas/.virtualenvs/payer/lib/python3.5/site-packages/django/utils/autoreload.py", line 226, in wrapper
    fn(*args, **kwargs)
  File "/home/alvas/.virtualenvs/payer/lib/python3.5/site-packages/django/__init__.py", line 18, in setup
    apps.populate(settings.INSTALLED_APPS)
  File "/home/alvas/.virtualenvs/payer/lib/python3.5/site-packages/django/apps/registry.py", line 108, in populate
    app_config.import_models(all_models)
  File "/home/alvas/.virtualenvs/payer/lib/python3.5/site-packages/django/apps/config.py", line 202, in import_models
    self.models_module = import_module(models_module_name)
  File "/home/alvas/.virtualenvs/payer/lib/python3.5/importlib/__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 986, in _gcd_import
  File "<frozen importlib._bootstrap>", line 969, in _find_and_load
  File "<frozen importlib._bootstrap>", line 958, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 673, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 662, in exec_module
  File "<frozen importlib._bootstrap>", line 222, in _call_with_frames_removed
  File "/home/alvas/data-project/myprojname/project/models.py", line 5, in <module>
    from myprojname.data import Sentence
ImportError: No module named 'myprojname.data'

如何连接来自不同应用的模型？

已编辑

当我在myprojname.project.models.py 中使用from data import Sentence 时，它会抛出一个ImportError：

Traceback (most recent call last):
  File "/home/alvas/.virtualenvs/statnlp/lib/python3.5/site-packages/django/utils/autoreload.py", line 226, in wrapper
    fn(*args, **kwargs)
  File "/home/alvas/.virtualenvs/statnlp/lib/python3.5/site-packages/django/core/management/commands/runserver.py", line 109, in inner_run
    autoreload.raise_last_exception()
  File "/home/alvas/.virtualenvs/statnlp/lib/python3.5/site-packages/django/utils/autoreload.py", line 249, in raise_last_exception
    six.reraise(*_exception)
  File "/home/alvas/.virtualenvs/statnlp/lib/python3.5/site-packages/django/utils/six.py", line 685, in reraise
    raise value.with_traceback(tb)
  File "/home/alvas/.virtualenvs/statnlp/lib/python3.5/site-packages/django/utils/autoreload.py", line 226, in wrapper
    fn(*args, **kwargs)

  File "/home/alvas/.virtualenvs/statnlp/lib/python3.5/site-packages/django/__init__.py", line 18, in setup
    apps.populate(settings.INSTALLED_APPS)
  File "/home/alvas/.virtualenvs/statnlp/lib/python3.5/site-packages/django/apps/registry.py", line 108, in populate
    app_config.import_models(all_models)
  File "/home/alvas/.virtualenvs/statnlp/lib/python3.5/site-packages/django/apps/config.py", line 202, in import_models
    self.models_module = import_module(models_module_name)
  File "/home/alvas/.virtualenvs/statnlp/lib/python3.5/importlib/__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 986, in _gcd_import
  File "<frozen importlib._bootstrap>", line 969, in _find_and_load
  File "<frozen importlib._bootstrap>", line 958, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 673, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 662, in exec_module
  File "<frozen importlib._bootstrap>", line 222, in _call_with_frames_removed
  File "/home/alvas/data-project/myprojname/project/models.py", line 5, in <module>
    from data import Sentence
ImportError: cannot import name 'Sentence'

【问题讨论】：

一个问题，当你可以做 from data.models import Sentence 时，为什么要相对导入？
非相对导入将是 from data.models import Sentence 而不是 from myprojname.data import Sentence
对不起，你不得不从 data.models 导入句子，我的错。
啊太棒了！现在可以from data.models import Sentence !!知道是什么让 Django 与普通 python 不同，因此它可以在不位于正确目录或相对导入中的情况下进行导入？
什么都没有。 Django 与这里的“普通 Python”没有任何不同。

标签： python django web-applications django-models orm

【解决方案1】：

您的导入应该是from data.models import Sentence 而不是from myprojname.data import Sentence。

【讨论】：

谢谢拉杰什！！！但是知道是什么让 Django 与普通 python 不同，这样它就可以在不位于正确目录或相对导入中的情况下进行导入？
这方面我不太确定。