django 外键model的互相读取方法

先设定一个关系模型如下：

from django.db import models
class Blog(models.Model):
 name = models.CharField(max_length=100)
 tagline = models.TextField()
 def __str__(self):   
  return self.name
 
class Author(models.Model):
 name = models.CharField(max_length=50)
 email = models.EmailField()
 def __str__(self):   
  return self.name
 
class Entry(models.Model):
 blog = models.ForeignKey(Blog)
 headline = models.CharField(max_length=255)
 body_text = models.TextField()
 authors = models.ManyToManyField(Author)
 def __str__(self):   
  return self.headline

上面的数据关系很明晰,Entry中有Blog和Author的外键,如果要在Entry中读取blog和author的数据很容易：

entry = Entry.objects.all()
for e in entry:
 blog = e.blog
 author = e.authors

要在Blog和Author中读取Entry也可以：

blog = Blog.objects.all()
entry = blog.entry_set.all()
 
author = Author.objects.all()
entry = author.entry_set.all()

下面通过entry使blog和author互相读取，比如要知道一个blog的Author只需如下：

blogs = Blog.objects.all()
for blog in blogs:
 if blog.name== “我们想要查询的博客的name”
  author = blog. entry_set.authors

要查询一个author的所有blog如下：

authors = Author.objects.all()
blogs = []
 
for author in authors:
 if author.name== “我们想要查询的Author的name”
  for entry in author.entry_set.all():
   blogs.append(entry. blog)