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()

There are other ways to initialize it:

app = Flask(__name__)
db = MongoAlchemy(app)

db = MongoAlchemy()
def init_app():
    app = Flask(__name__)
    db.init_app(app)
    return app

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()

You can create your own queries:

from flask.ext.mongoalchemy import BaseQuery
from application import db
 
class MyCustomizedQuery(BaseQuery):
 
    def get_johns(self):
        return self.filter(self.type.first_name == 'John')
 
class Person(db.Document):
    query_class = MyCustomizedQuery
    name = db.StringField()

There are other functions:

• first_or_404()
• get(mongo_id)
• get_or_404(mongo_id)

You can call a method for a query: paginate(page, per_page=20, error_out=True). This method returns a Pagination object in which you can call…

• has_next()
• has_prev()
• items = None
• next(error_out=False)
• next_num
• page = None
• pages
• per_page = None
• prev(error_out=False)
• prev_num
• query = None
• total = None

Documentation for these methods

>>> app.config['MONGOALCHEMY_SERVER_AUTH'] = False

There are values to change in Mongo config:

• MONGOALCHEMY_DATABASE
• MONGOALCHEMY_SERVER
• MONGOALCHEMY_PORT
• MONGOALCHEMY_USER
• MONGOALCHEMY_PASSWORD
• MONGOALCHEMY_SAFE_SESSION
• MONGOALCHEMY_OPTIONS
• MONGOALCHEMY_SERVER_AUTH
• MONGOALCHEMY_REPLICA_SET
• MONGOALCHEMY_CONNECTION_STRING

When MongoAlchemy or init_app() are invoked with only one argument (the Flask instance), a configuration value prefix of MONGOALCHEMY is assumed; this can be overridden with the config_prefix argument, for example:

app = Flask(__name__)
# defaulting to MONGOENGINE prefix
mongo1 = MongoAlchemy(app)
# using another database config
app.config['OTHER_DBNAME'] = 'other'
mongo2 = MongoAlchemy(app, config_prefix='OTHER')