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)

来源：https://blog.csdn.net/JackieLeeWelas/article/details/50311077