class BlogPost(Document):
    title = StringField(required=True, max_length=200)
    posted = DateTimeField(default=datetime.datetime.now)
    tags = ListField(StringField(max_length=50))

class TextPost(BlogPost):
    content = StringField(required=True)

class LinkPost(BlogPost):
    url = StringField(required=True)

# Create a text-based post
>>> post1 = TextPost(title='Using MongoEngine', content='See the tutorial')
>>> post1.tags = ['mongodb', 'mongoengine']
>>> post1.save()

# Create a link-based post
>>> post2 = LinkPost(title='MongoEngine Docs', url='hmarr.com/mongoengine')
>>> post2.tags = ['mongoengine', 'documentation']
>>> post2.save()

# Iterate over all posts using the BlogPost superclass
>>> for post in BlogPost.objects:
...     print '===', post.title, '==='
...     if isinstance(post, TextPost):
...         print post.content
...     elif isinstance(post, LinkPost):
...         print 'Link:', post.url
...     print
...
=== Using MongoEngine ===
See the tutorial

=== MongoEngine Docs ===
Link: hmarr.com/mongoengine

>>> len(BlogPost.objects)
2
>>> len(HtmlPost.objects)
1
>>> len(LinkPost.objects)
1

# Find tagged posts
>>> len(BlogPost.objects(tags='mongoengine'))
2
>>> len(BlogPost.objects(tags='mongodb'))
1