=================================================================
sqlitedict -- persistent dict, backed-up by SQLite and pickle
=================================================================, Travis, _, License, _

.., Travis, image:: https://travis-ci.org/RaRe-Technologies/sqlitedict.svg?branch=master
.., Downloads, image:: https://img.shields.io/pypi/dm/sqlitedict.svg
.., License, image:: https://img.shields.io/pypi/l/sqlitedict.svg
.. _Travis: https://travis-ci.org/RaRe-Technologies/sqlitedict
.. _Downloads: https://pypi.python.org/pypi/sqlitedict
.. _License: https://pypi.python.org/pypi/sqlitedict

A lightweight wrapper around Python's sqlite3 database with a simple, Pythonic
dict-like interface and support for multi-thread access:

.. code-block:: python

from sqlitedict import SqliteDict
mydict = SqliteDict('./my_db.sqlite', autocommit=True)
mydict['some_key'] = any_picklable_object
print mydict['some_key'] # prints the new value
for key, value in mydict.iteritems():
print key, value
print len(mydict) # etc... all dict functions work
mydict.close()

Pickle is used internally to (de)serialize the values. Keys are arbitrary strings,
values arbitrary pickle-able objects.

If you don't use autocommit (default is no autocommit for performance), then
don't forget to call mydict.commit() when done with a transaction:

.. code-block:: python

using SqliteDict as context manager works too (RECOMMENDED)

with SqliteDict('./my_db.sqlite') as mydict: # note no autocommit=True
... mydict['some_key'] = u"first value"
... mydict['another_key'] = range(10)
... mydict.commit()
... mydict['some_key'] = u"new value"
... # no explicit commit here
with SqliteDict('./my_db.sqlite') as mydict: # re-open the same DB
... print mydict['some_key'] # outputs 'first value', not 'new value'

Features

• Values can be any picklable objects (uses cPickle with the highest protocol).

• Support for multiple tables (=dicts) living in the same database file.

• Support for access from multiple threads to the same connection (needed by e.g. Pyro).
  Vanilla sqlite3 gives you ProgrammingError: SQLite objects created in a thread can only be used in that same thread.

  Concurrent requests are still serialized internally, so this "multithreaded support"
  doesn't give you any performance benefits. It is a work-around for sqlite limitations in Python.

• Support for custom serialization or compression:

  .. code-block:: python

  # use JSON instead of pickle
  >>> import json
  >>> mydict = SqliteDict('./my_db.sqlite', encode=json.dumps, decode=json.loads)
  
  # apply zlib compression after pickling
  >>> import zlib, pickle, sqlite3
  >>> def my_encode(obj):
  ...     return sqlite3.Binary(zlib.compress(pickle.dumps(obj, pickle.HIGHEST_PROTOCOL)))
  >>> def my_decode(obj):
  ...     return pickle.loads(zlib.decompress(bytes(obj)))
  >>> mydict = SqliteDict('./my_db.sqlite', encode=my_encode, decode=my_decode)
  

Installation

The module has no dependencies beyond Python itself. The minimum Python version is 2.5, continuously tested on Python 2.6, 2.7, 3.3 and 3.4 on Travis <https://travis-ci.org/RaRe-Technologies/sqlitedict>_.

Install or upgrade with::

pip install -U sqlitedict

or from the source tar.gz <http://pypi.python.org/pypi/sqlitedict>_::

python setup.py install

Documentation

Standard Python document strings are inside the module:

.. code-block:: python

import sqlitedict
help(sqlitedict)

(but it's just dict with a commit, really).

Beware: because of Python semantics, sqlitedict cannot know when a mutable
SqliteDict-backed entry was modified in RAM. For example, mydict.setdefault('new_key', []).append(1)
will leave mydict['new_key'] equal to empty list, not [1]. You'll need to
explicitly assign the mutated object back to SqliteDict to achieve the same effect:

.. code-block:: python

val = mydict.get('new_key', [])
val.append(1) # sqlite DB not updated here!
mydict['new_key'] = val # now updated

For developers

Install::

# pip install nose
# pip install coverage

To perform all tests::

make test-all

To perform all tests with coverage::

make test-all-with-coverage

Comments, bug reports

sqlitedict resides on github <https://github.com/RaRe-Technologies/sqlitedict>_. You can file
issues or pull requests there.

sqlitedict is open source software released under the Apache 2.0 license <http://opensource.org/licenses/apache2.0.php>.
Copyright (c) 2011-now Radim Řehůřek <http://radimrehurek.com> and contributors.