pip install Flask-MongoAlchemy

from flask import Flask
from flask.ext.mongoalchemy import MongoAlchemy
app = Flask(__name__)
app.config['MONGOALCHEMY_DATABASE'] = 'library'
db = MongoAlchemy(app)
 
class Author(db.Document):
    name = db.StringField()
 
class Book(db.Document):
    title = db.StringField()
    author = db.DocumentField(Author)
    year = db.IntField()

Now you can create authors and books:

>>> from application import Author, Book
>>> mark_pilgrim = Author(name='Mark Pilgrim')
>>> dive = Book(title='Dive Into Python', author=mark_pilgrim, year=2004)
>>> mark_pilgrim.save()
>>> dive.save()

If you make any changes on a document, you may call save() again:

>>> mark_pilgrim.name = 'Mark Stalone'
>>> mark_pilgrim.save()

And you can remove a document from the database by calling its remove() method:

>>> dive.remove()

Every document has a query class property. It’s very simple to use it:

>>> mark = Author.query.get('76726')
>>> mark.name = 'Mark Pilgrim'
>>> mark.save()

You also can use the filter method instead of the get() method:

>>> mark = Author.query.filter(Author.name == 'Mark Pilgrim').first()
>>> mark.name = 'Steve Jobs'
>>> mark.save()