如何在Django中向具有多个外键的关系添加数据？

Question

我正在用Python构建一个模拟程序，想用Django的ORM来把（中间和最终的）结果存储到数据库里。所以我不太关心网址和视图。

我遇到的问题是，如何创建一个包含多个外键的对象。这个对象应该表示一个代理和一个时间步骤之间的关系。

以下是我的代码：

我使用了以下模型：

from django.db import models
import random
from django.contrib.admin.util import related_name

# Create your models here.
class Agent(models.Model):

    agent = int
    def __init__(self, agent, *args, **kwargs):
        models.Model.__init__(self, *args, **kwargs)
        self.agent = agent

    def __str__(self):
        return str(self.agent)

class Step(models.Model):

    step = int

    def __init__(self, step, *args, **kwargs):
        models.Model.__init__(self, *args, **kwargs)
        self.step = step

    def __str__(self):
        return str(self.step)


class StepAgentData(models.Model):

    def __init__(self, step, agent, *args, **kwargs):
        models.Model.__init__(self, *args, **kwargs)
        self.step = step  #This does not work
        self.agent = agent

    step = models.ForeignKey(Step, related_name='time_step')
    agent = models.ForeignKey(Agent, related_name='associated_agent')
    data = float    

    def __unicode__(self):
        return str("Step %s \t Agent %s ", (self.step,self.agent))

运行以下脚本：

from DBStructureTest.App.models import Step, Agent, StepAgentData

if __name__ == '__main__':
    s = Step(1)
    s.save()
    a = Agent(2)
    a.save()
    sad = StepAgentData(s,a)
    sad.save()

    print "finished"

在执行StepAgentData构造函数中的self.step = step时，会出现以下错误信息（请查看StepAgentData模型中的注释）：

>  File
> "/usr/local/lib/python2.7/dist-packages/django/db/models/fields/related.py",
> line 367, in __set__
>     val = getattr(value, self.field.rel.get_related_field().attname)  
> File
> "/usr/local/lib/python2.7/dist-packages/django/db/models/fields/related.py",
> line 773, in get_related_field
>     data = self.to._meta.get_field_by_name(self.field_name)   File
> "/usr/local/lib/python2.7/dist-packages/django/db/models/options.py",
> line 307, in get_field_by_name
>     cache = self.init_name_map()   File
> "/usr/local/lib/python2.7/dist-packages/django/db/models/options.py",
> line 337, in init_name_map
>     for f, model in self.get_all_related_m2m_objects_with_model():  
> File
> "/usr/local/lib/python2.7/dist-packages/django/db/models/options.py",
> line 414, in get_all_related_m2m_objects_with_model
>     cache = self._fill_related_many_to_many_cache()   File
> "/usr/local/lib/python2.7/dist-packages/django/db/models/options.py",
> line 428, in _fill_related_many_to_many_cache
>     for klass in get_models():   File
> "/usr/local/lib/python2.7/dist-packages/django/db/models/loading.py",
> line 167, in get_models
>     self._populate()   File
> "/usr/local/lib/python2.7/dist-packages/django/db/models/loading.py",
> line 61, in _populate
>     self.load_app(app_name, True)   File
> "/usr/local/lib/python2.7/dist-packages/django/db/models/loading.py",
> line 76, in load_app
>     app_module = import_module(app_name)   File
> "/usr/local/lib/python2.7/dist-packages/django/utils/importlib.py",
> line 35, in import_module
>     __import__(name) ImportError: No module named App

文件夹结构如下：

|-DBStructureTest
    |-App
        |-__init__.py       
        |-Main.py
        |-models.py
        |-test.py
        |-views.py
    |-__init__.py
    |-manage.py
    |-settings.py
    |-urls.py

我哪里做错了？非常感谢任何帮助。

编辑：在/App目录下，我在执行'import models'后得到了以下信息：

import models Traceback (most recent call last): File "", line 1, in File "models.py", line 1, in from django.db import models File "/usr/local/lib/python2.7/dist-packages/django/db/init.py", line 14, in if not settings.DATABASES: File "/usr/local/lib/python2.7/dist-packages/django/utils/functional.py", line 276, in getattr self._setup() File "/usr/local/lib/python2.7/dist-packages/django/conf/init.py", line 40, in _setup raise ImportError("Settings cannot be imported, because environment variable %s is undefined." % ENVIRONMENT_VARIABLE) ImportError: Settings cannot be imported, because environment variable DJANGO_SETTINGS_MODULE is undefined. '

数据库 django 错误处理 orm 环境变量模型外键代理

如何在Django中向具有多个外键的关系添加数据？

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