=================================================================
sqlitedict -- persistent ``dict``, backed-up by SQLite and pickle
=================================================================

|Travis|_
|Downloads|_
|License|_

.. |Travis| image:: https://img.shields.io/travis/piskvorky/sqlitedict.svg
.. |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/piskvorky/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.

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/piskvorky/sqlitedict>`_.

Install or upgrade with::

    easy_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/piskvorky/sqlitedict>`_. You can file
issues or pull requests there.

History
-------

**1.4.0**: fix regression where iterating over keys/values/items returned a full list instead of iterator

**1.3.0**: improve error handling in multithreading (`PR #28 <https://github.com/piskvorky/sqlitedict/pull/28>`_); 100% test coverage.

**1.2.0**: full python 3 support, continuous testing via `Travis CI <https://travis-ci.org/piskvorky/sqlitedict>`_.

----

``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.