Django Queryset of related objects, after prefiltering on original model

Question

Given a queryset for one model, I want to get a queryset of another model that is related by foreign key. Take the Django project docs' weblog schema:

class Blog(models.Model):
    name = models.CharField(max_length=100)
    tagline = models.TextField()

    def __unicode__(self):
        return self.name

class Author(models.Model):
    name = models.CharField(max_length=50)
    email = models.EmailField()

    def __unicode__(self):
        return self.name

class Entry(models.Model):
    blog = models.ForeignKey(Blog)
    headline = models.CharField(max_length=255)
    body_text = models.TextField()
    pub_date = models.DateField()
    mod_date = models.DateField()
    authors = models.ManyToManyField(Author)
    n_comments = models.IntegerField()
    n_pingbacks = models.IntegerField()
    rating = models.IntegerField()

    def __unicode__(self):
        return self.headline

Suppose I have an author object, and I want to get every blog that author has written for, as a queryset. I do something like author_blogs = [entry.blog for entry in author.entry_set]. But I'm left with a list in this case, not a queryset. Is there a way I can do this directly with ORM queries, so I can set it up via a custom Entry manager with use_for_related_fields = True and do something like author_blogs = author.entry_set.blogs, and get the benefits of delayed evaluation, etc., of a queryset?

Edited scenario and solution

So, I realized after the fact that the application of my question is slightly different than how I posed it above, for which Daniel Roseman's situation makes a lot of sense. My situation is really more like author.entry_set.manager_method().blogs, where manager_method() returns a queryset of Entry objects. I accepted his answer because it inspired the solution I found which is to do:

author_blogs = Blog.objects.filter(entry__in=author.entry_set.manager_method())

The nice thing is that it only uses one DB query. It's a bit tricky and verbose, so I think it's best to define blogs() as an object method of Author, returning the above.

Answer 1

The trick for this is to remember that if you want a queryset of Blogs, you should start with the Blog model. Then, you can use the double-underscore syntax to follow relations. So:

author_blogs = Blog.objects.filter(entry__authors=author)