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Flask-MongoEngine is a Flask extension that provides integration with MongoEngine and WTF model forms.

Project Description

A Flask extension that provides integration with `MongoEngine <>`_.
For more information on MongoEngine please check out the `MongoEngine Documentation <>`_.

It handles connection management for your app.
You can also use `WTForms <>`_ as model forms for your models.

Installing Flask-MongoEngine

Install with **pip**::

pip install flask-mongoengine


Basic setup is easy, just fetch the extension::

from flask import Flask
from flask_mongoengine import MongoEngine

app = Flask(__name__)
db = MongoEngine(app)

Or, if you are setting up your database before your app is initialized, as is the case with application factories::

from flask import Flask
from flask_mongoengine import MongoEngine
db = MongoEngine()
app = Flask(__name__)

By default, Flask-MongoEngine assumes that the :program:`mongod` instance is running
on **localhost** on port **27017**, and you wish to connect to the database named **test**.

If MongoDB is running elsewhere, you should provide the :attr:`host` and :attr:`port` settings
in the `'MONGODB_SETTINGS'` dictionary wih `app.config`.::

app.config['MONGODB_SETTINGS'] = {
'db': 'project1',
'host': '',
'port': 12345

If the database requires authentication, the :attr:`username` and :attr:`password`
arguments should be provided `'MONGODB_SETTINGS'` dictionary wih `app.config`.::

app.config['MONGODB_SETTINGS'] = {
'db': 'project1',

Uri style connections are also supported, just supply the uri as the :attr:`host`
in the `'MONGODB_SETTINGS'` dictionary with `app.config`. **Note that database name from uri has priority over name.** ::

app.config['MONGODB_SETTINGS'] = {
'db': 'project1',
'host': 'mongodb://localhost/database_name'

Connection settings may also be provided individually by prefixing the setting with `'MONGODB_'` in the `app.config`.::

app.config['MONGODB_DB'] = 'project1'
app.config['MONGODB_HOST'] = ''
app.config['MONGODB_PORT'] = 12345
app.config['MONGODB_USERNAME'] = 'webapp'
app.config['MONGODB_PASSWORD'] = 'pwd123'

Custom Queryset

flask-mongoengine attaches the following methods to Mongoengine's default QuerySet:

* **get_or_404**: works like .get(), but calls abort(404) if the object DoesNotExist.
* **first_or_404**: same as above, except for .first().
* **paginate**: paginates the QuerySet. Takes two arguments, *page* and *per_page*.
* **paginate_field**: paginates a field from one document in the QuerySet.
Arguments: *field_name*, *doc_id*, *page*, *per_page*.


# 404 if object doesn't exist
def view_todo(todo_id):
todo = Todo.objects.get_or_404(_id=todo_id)

# Paginate through todo
def view_todos(page=1):
paginated_todos = Todo.objects.paginate(page=page, per_page=10)

# Paginate through tags of todo
def view_todo_tags(todo_id, page=1):
todo = Todo.objects.get_or_404(_id=todo_id)
paginated_tags = todo.paginate_field('tags', page, per_page=10)

Properties of the pagination object include: iter_pages, next, prev, has_next,
has_prev, next_num, prev_num.

In the template::

{# Display a page of todos #}
{% for todo in paginated_todos.items %}
<li>{{ todo.title }}</li>
{% endfor %}

{# Macro for creating navigation links #}
{% macro render_navigation(pagination, endpoint) %}
<div class=pagination>
{% for page in pagination.iter_pages() %}
{% if page %}
{% if page != %}
<a href="{{ url_for(endpoint, page=page) }}">{{ page }}</a>
{% else %}
<strong>{{ page }}</strong>
{% endif %}
{% else %}
<span class=ellipsis>…</span>
{% endif %}
{% endfor %}
{% endmacro %}

{{ render_navigation(paginated_todos, 'view_todos') }}

MongoEngine and WTForms

flask-mongoengine automatically generates WTForms from MongoEngine models::

from import model_form

class User(db.Document):
email = db.StringField(required=True)
first_name = db.StringField(max_length=50)
last_name = db.StringField(max_length=50)

class Content(db.EmbeddedDocument):
text = db.StringField()
lang = db.StringField(max_length=3)

class Post(db.Document):
title = db.StringField(max_length=120, required=True, validators=[validators.InputRequired(message=u'Missing title.'),])
author = db.ReferenceField(User)
tags = db.ListField(db.StringField(max_length=30))
content = db.EmbeddedDocumentField(Content)

PostForm = model_form(Post)

def add_post(request):
form = PostForm(request.POST)
if request.method == 'POST' and form.validate():
# do something
return render_template('add_post.html', form=form)

For each MongoEngine field, the most appropriate WTForm field is used.
Parameters allow the user to provide hints if the conversion is not implicit::

PostForm = model_form(Post, field_args={'title': {'textarea': True}})

Supported parameters:

For fields with `choices`:

- `multiple` to use a SelectMultipleField
- `radio` to use a RadioField

For `StringField`:

- `password` to use a PasswordField
- `textarea` to use a TextAreaField

(By default, a StringField is converted into a TextAreaField if and only if it has no max_length.)

Supported fields

* StringField
* BinaryField
* URLField
* EmailField
* IntField
* FloatField
* DecimalField
* BooleanField
* DateTimeField
* **ListField** (using wtforms.fields.FieldList )
* SortedListField (duplicate ListField)
* **EmbeddedDocumentField** (using wtforms.fields.FormField and generating inline Form)
* **ReferenceField** (using wtforms.fields.SelectFieldBase with options loaded from QuerySet or Document)
* DictField

Not currently supported field types:

* ObjectIdField
* GeoLocationField
* GenericReferenceField

Session Interface

To use MongoEngine as your session store simple configure the session interface::

from flask_mongoengine import MongoEngine, MongoEngineSessionInterface

app = Flask(__name__)
db = MongoEngine(app)
app.session_interface = MongoEngineSessionInterface(db)

Debug Toolbar Panel

.. image:: _static/debugtoolbar.png
:target: #debug-toolbar-panel

If you use the Flask-DebugToolbar you can add
`'flask_mongoengine.panels.MongoDebugPanel'` to the `DEBUG_TB_PANELS` config
list and then it will automatically track your queries::

from flask import Flask
from flask_debugtoolbar import DebugToolbarExtension

app = Flask(__name__)
app.config['DEBUG_TB_PANELS'] = ['flask_mongoengine.panels.MongoDebugPanel']
db = MongoEngine(app)
toolbar = DebugToolbarExtension(app)


0.6 to 0.7

`ListFieldPagination` order of arguments have been changed to be more logical::

# Old order
ListFieldPagination(self, queryset, field_name, doc_id, page, per_page, total)

# New order
ListFieldPagination(self, queryset, doc_id, field_name, page, per_page, total)


Inspired by two repos:

`danjac <>`_
`maratfm <>`_
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