Flask-PyMongo

MongoDB is an open source database that stores flexible JSON-like “documents,” which can have any number, name, or hierarchy of fields within, instead of rows of data as in a relational database. Python developers can think of MongoDB as a persistent, searchable repository of Python dictionaries (and, in fact, this is how PyMongo represents MongoDB documents).

Flask-PyMongo bridges Flask and PyMongo, so that you can use Flask’s normal mechanisms to configure and connect to MongoDB.

Quickstart

First, install Flask-PyMongo:

$ pip install Flask-PyMongo

Flask-PyMongo depends, and will install for you, recent versions of Flask (0.8 or later) and PyMongo (2.4 or later). Flask-PyMongo is compatible with and tested on Python 2.6, 2.7, and 3.3.

Next, add a PyMongo to your code:

from flask import Flask
from flask.ext.pymongo import PyMongo

app = Flask(__name__)
mongo = PyMongo(app)

PyMongo connects to the MongoDB server running on port 27017 on localhost, and assumes a default database name of app.name (i.e. whatever name you pass to Flask). This database is exposed as the db attribute.

You can use db directly in views:

@app.route('/')
def home_page():
    online_users = mongo.db.users.find({'online': True})
    return render_template('index.html',
        online_users=online_users)

Helpers

Flask-PyMongo provides helpers for some common tasks:

Collection.find_one_or_404(*args, **kwargs)

Find and return a single document, or raise a 404 Not Found exception if no document matches the query spec. See find_one() for details.

@app.route('/user/<username>')
def user_profile(username):
    user = mongo.db.users.find_one_or_404({'_id': username})
    return render_template('user.html',
        user=user)
PyMongo.send_file(filename, base='fs', version=-1, cache_for=31536000)

Return an instance of the response_class containing the named file, and implement conditional GET semantics (using make_conditional()).

@app.route('/uploads/<path:filename>')
def get_upload(filename):
    return mongo.send_file(filename)
Parameters:
  • filename (str) – the filename of the file to return
  • base (str) – the base name of the GridFS collections to use
  • version (bool) – if positive, return the Nth revision of the file identified by filename; if negative, return the Nth most recent revision. If no such version exists, return with HTTP status 404.
  • cache_for (int) – number of seconds that browsers should be instructed to cache responses
PyMongo.save_file(filename, fileobj, base='fs', content_type=None)

Save the file-like object to GridFS using the given filename. Returns None.

@app.route('/uploads/<path:filename>', methods=['POST'])
def save_upload(filename):
    mongo.save_file(filename, request.files['file'])
    return redirect(url_for('get_upload', filename=filename))
Parameters:
  • filename (str) – the filename of the file to return
  • fileobj (file) – the file-like object to save
  • base (str) – base the base name of the GridFS collections to use
  • content_type (str) – the MIME content-type of the file. If None, the content-type is guessed from the filename using guess_type()
class flask_pymongo.BSONObjectIdConverter(map)

A simple converter for the RESTful URL routing system of Flask.

@app.route('/<ObjectId:task_id>')
def show_task(task_id):
    task = mongo.db.tasks.find_one_or_404(task_id)
    return render_template('task.html', task=task)

Valid object ID strings are converted into ObjectId objects; invalid strings result in a 404 error. The converter is automatically registered by the initialization of PyMongo with keyword ObjectId.

Configuration

PyMongo understands the following configuration directives:

MONGO_URI A MongoDB URI which is used in preference of the other configuration variables.
MONGO_HOST The host name or IP address of your MongoDB server. Default: “localhost”.
MONGO_PORT The port number of your MongoDB server. Default: 27017.
MONGO_AUTO_START_REQUEST Set to False to disable PyMongo 2.2’s “auto start request” behavior (see MongoClient). Default: True.
MONGO_MAX_POOL_SIZE (optional): The maximum number of idle connections maintained in the PyMongo connection pool. Default: PyMongo default.
MONGO_SOCKET_TIMEOUT_MS (optional): (integer) How long (in milliseconds) a send or receive on a socket can take before timing out. Default: PyMongo default.
MONGO_CONNECT_TIMEOUT_MS (optional): (integer) How long (in milliseconds) a connection can take to be opened before timing out. Default: PyMongo default.
MONGO_DBNAME The database name to make available as the db attribute. Default: app.name.
MONGO_USERNAME The user name for authentication. Default: None
MONGO_PASSWORD The password for authentication. Default: None
MONGO_REPLICA_SET The name of a replica set to connect to; this must match the internal name of the replica set (as deteremined by the isMaster command). Default: None.
MONGO_READ_PREFERENCE Determines how read queries are routed to the replica set members. Must be one of the constants defined on pymongo.read_preferences.ReadPreference or the string names thereof
MONGO_DOCUMENT_CLASS This tells pymongo to return custom objects instead of dicts, for example bson.son.SON. Default: dict

When PyMongo or init_app() are invoked with only one argument (the Flask instance), a configuration value prefix of MONGO is assumed; this can be overridden with the config_prefix argument.

This technique can be used to connect to multiple databases or database servers:

app = Flask(__name__)

# connect to MongoDB with the defaults
mongo1 = PyMongo(app)

# connect to another MongoDB database on the same host
app.config['MONGO2_DBNAME'] = 'dbname_two'
mongo2 = PyMongo(app, config_prefix='MONGO2')

# connect to another MongoDB server altogether
app.config['MONGO3_HOST'] = 'another.host.example.com'
app.config['MONGO3_PORT'] = 27017
app.config['MONGO3_DBNAME'] = 'dbname_three'
mongo3 = PyMongo(app, config_prefix='MONGO3')

Some auto-configured settings that you should be aware of are:

tz_aware:
Flask-PyMongo always uses timezone-aware datetime objects. That is, it sets the tz_aware parameter to True when creating a connection. The timezone of datetime objects returned from MongoDB will always be UTC.
safe:
Flask-PyMongo sets “safe” mode by default, which causes save(), insert(), update(), and remove() to wait for acknowledgement from the server before returning. You may override this on a per-call basis by passing the keyword argument safe=False to any of the effected methods.

API

Constants

flask_pymongo.ASCENDING = 1

Ascending sort order.

flask_pymongo.DESCENDING = -1

Descending sort order.

Classes

class flask_pymongo.PyMongo(app=None, config_prefix='MONGO')

Automatically connects to MongoDB using parameters defined in Flask configuration.

cx

The automatically created Connection or ReplicaSetConnection object.

db

The automatically created Database object corresponding to the provided MONGO_DBNAME configuration parameter.

init_app(app, config_prefix='MONGO')

Initialize the app for use with this PyMongo. This is called automatically if app is passed to __init__().

The app is configured according to the configuration variables PREFIX_HOST, PREFIX_PORT, PREFIX_DBNAME, PREFIX_AUTO_START_REQUEST, PREFIX_REPLICA_SET, PREFIX_READ_PREFERENCE, PREFIX_USERNAME, PREFIX_PASSWORD, and PREFIX_URI where “PREFIX” defaults to “MONGO”. If PREFIX_URL is set, it is assumed to have all appropriate configurations, and the other keys are overwritten using their values as present in the URI.

Parameters:
  • app (flask.Flask) – the application to configure for use with this PyMongo
  • config_prefix (str) – determines the set of configuration variables used to configure this PyMongo
save_file(filename, fileobj, base='fs', content_type=None)

Save the file-like object to GridFS using the given filename. Returns None.

@app.route('/uploads/<path:filename>', methods=['POST'])
def save_upload(filename):
    mongo.save_file(filename, request.files['file'])
    return redirect(url_for('get_upload', filename=filename))
Parameters:
  • filename (str) – the filename of the file to return
  • fileobj (file) – the file-like object to save
  • base (str) – base the base name of the GridFS collections to use
  • content_type (str) – the MIME content-type of the file. If None, the content-type is guessed from the filename using guess_type()
send_file(filename, base='fs', version=-1, cache_for=31536000)

Return an instance of the response_class containing the named file, and implement conditional GET semantics (using make_conditional()).

@app.route('/uploads/<path:filename>')
def get_upload(filename):
    return mongo.send_file(filename)
Parameters:
  • filename (str) – the filename of the file to return
  • base (str) – the base name of the GridFS collections to use
  • version (bool) – if positive, return the Nth revision of the file identified by filename; if negative, return the Nth most recent revision. If no such version exists, return with HTTP status 404.
  • cache_for (int) – number of seconds that browsers should be instructed to cache responses
class flask_pymongo.wrappers.Collection(database, name, create=False, **kwargs)

Custom sub-class of pymongo.collection.Collection which adds Flask-specific helper methods.

find_one_or_404(*args, **kwargs)

Find and return a single document, or raise a 404 Not Found exception if no document matches the query spec. See find_one() for details.

@app.route('/user/<username>')
def user_profile(username):
    user = mongo.db.users.find_one_or_404({'_id': username})
    return render_template('user.html',
        user=user)

Wrappers

These classes exist solely in order to make expressions such as mongo.db.foo.bar evaluate to a Collection instance instead of a pymongo.collection.Collection instance. They are documented here solely for completeness.

class flask_pymongo.wrappers.MongoClient(host=None, port=None, max_pool_size=100, document_class=<type 'dict'>, tz_aware=False, _connect=True, **kwargs)

Returns instances of flask_pymongo.wrappers.Database instead of pymongo.database.Database when accessed with dot notation.

class flask_pymongo.wrappers.MongoReplicaSetClient(hosts_or_uri=None, max_pool_size=100, document_class=<type 'dict'>, tz_aware=False, _connect=True, **kwargs)

Returns instances of flask_pymongo.wrappers.Database instead of pymongo.database.Database when accessed with dot notation.

class flask_pymongo.wrappers.Database(connection, name)

Returns instances of flask_pymongo.wrappers.Collection instead of pymongo.collection.Collection when accessed with dot notation.

History and Contributors

Changes:

  • 0.3.0: July 4, 2013
    • This is a minor version bump which introduces backwards breaking changes! Please read these change notes carefully.
    • Removed read preference constants from Flask-PyMongo; to set a read preference, use the string name or import contants directly from pymongo.read_preferences.ReadPreference.
    • #22 (partial) Add support for MONGO_SOCKET_TIMEOUT_MS and MONGO_CONNECT_TIMEOUT_MS options (ultrabug).
    • #27 (partial) Make Flask-PyMongo compatible with Python 3 (Vizzy).
  • 0.2.1: December 22, 2012
    • #19 Added MONGO_DOCUMENT_CLASS config option (jeverling).
  • 0.2.0: December 15, 2012
    • This is a minor version bump which may introduce backwards breaking changes! Please read these change notes carefully.
    • #17 Now using PyMongo 2.4’s MongoClient and MongoReplicaSetClient objects instead of Connection and ReplicaSetConnection classes (tang0th).
    • #17 Now requiring at least PyMongo version 2.4 (tang0th).
    • #17 The wrapper class flask_pymongo.wrappers.Connection is renamed to flask_pymongo.wrappers.MongoClient (tang0th).
    • #17 The wrapper class flask_pymongo.wrappers.ReplicaSetConnection is renamed to flask_pymongo.wrappers.MongoReplicaSetClient (tang0th).
    • #18 MONGO_AUTO_START_REQUEST now defaults to False when connecting using a URI.
  • 0.1.4: December 15, 2012
    • #15 Added support for MONGO_MAX_POOL_SIZE (Fabrice Aneche)
  • 0.1.3: September 22, 2012
    • Added support for configuration from MongoDB URI.
  • 0.1.2: June 18, 2012
    • Updated wiki example application
    • #14 Added examples and docs to PyPI package.
  • 0.1.1: May 26, 2012
    • Added support for PyMongo 2.2’s “auto start request” feature, by way of the MONGO_AUTO_START_REQUEST configuration flag.
    • #13 Added BSONObjectIdConverter (Christoph Herr)
    • #12 Corrected documentation typo (Thor Adam)
  • 0.1: December 21, 2011
    • Initial Release

Contributors:

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