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 intstall Flask-PyMongo

Flask-PyMongo depends, and will install for you, recent versions of Flask (0.8 or later) and PyMongo (2.1 or later).

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:

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

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()`

Configuration¶

PyMongo understands the following configuration directives:

`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_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 `PRIMARY`, `SECONDARY`, or `SECONDARY_ONLY`, or the string names thereof. Default `PRIMARY`.

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``s 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.

flask_pymongo.PRIMARY = 0¶: Send all queries to the replica set primary, and fail if none exists.

flask_pymongo.SECONDARY = 1¶: Distribute queries among replica set secondaries unless none exist or are up, in which case send queries to the primary.

flask_pymongo.SECONDARY_ONLY = 2¶: Distribute queries among replica set secondaries, and fail if none exist.

Classes¶

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

Automatically connects to MongoDB using parameters defined in Flask configuration named MONGO_HOST, MONGO_PORT, and MONGO_DBNAME.

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_REPLICA_SET, PREFIX_READ_PREFERENCE, PREFIX_USERNAME, and PREFIX_PASSWORD where “PREFIX” defaults to “MONGO”.

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:

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

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, options=None, 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.Connection(host=None, port=None, max_pool_size=10, network_timeout=None, 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.ReplicaSetConnection(hosts_or_uri=None, max_pool_size=10, document_class=<type 'dict'>, tz_aware=False, **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.