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klepto: persistent caching to memory, disk, or database
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About Klepto
============

``klepto`` extends python's ``lru_cache`` to utilize different keymaps and
alternate caching algorithms, such as ``lfu_cache`` and ``mru_cache``.
While caching is meant for fast access to saved results, ``klepto`` also
has archiving capabilities, for longer-term storage. ``klepto`` uses a
simple dictionary-sytle interface for all caches and archives, and all
caches can be applied to any python function as a decorator. Keymaps
are algorithms for converting a function's input signature to a unique
dictionary, where the function's results are the dictionary value.
Thus for ``y = f(x)``, ``y`` will be stored in ``cache[x]`` (e.g. ``{x:y}``).

``klepto`` provides both standard and *"safe"* caching, where *"safe"* caches
are slower but can recover from hashing errors. ``klepto`` is intended
to be used for distributed and parallel computing, where several of
the keymaps serialize the stored objects. Caches and archives are
intended to be read/write accessible from different threads and
processes. ``klepto`` enables a user to decorate a function, save the
results to a file or database archive, close the interpreter,
start a new session, and reload the function and it's cache.

``klepto`` is part of ``pathos``, a python framework for heterogenous computing.
``klepto`` is in active development, so any user feedback, bug reports, comments,
or suggestions are highly appreciated.  A list of known issues is maintained
at http://trac.mystic.cacr.caltech.edu/project/pathos/query.html, with a public
ticket list at https://github.com/uqfoundation/klepto/issues.


Major Features
==============

``klepto`` has standard and *"safe"* variants of the following:

    - ``lfu_cache`` - the least-frequently-used caching algorithm
    - ``lru_cache`` - the least-recently-used caching algorithm
    - ``mru_cache`` - the most-recently-used caching algorithm
    - ``rr_cache`` - the random-replacement caching algorithm
    - ``no_cache`` - a dummy caching interface to archiving
    - ``inf_cache`` - an infinitely-growing cache

``klepto`` has the following archive types:

    - ``file_archive`` - a dictionary-style interface to a file
    - ``dir_archive`` - a dictionary-style interface to a folder of files
    - ``sqltable_archive`` - a dictionary-style interface to a sql database table
    - ``sql_archive`` - a dictionary-style interface to a sql database
    - ``hdfdir_archive`` - a dictionary-style interface to a folder of hdf5 files
    - ``hdf_archive`` - a dictionary-style interface to a hdf5 file
    - ``dict_archive`` - a dictionary with an archive interface
    - ``null_archive`` - a dictionary-style interface to a dummy archive 

``klepto`` provides the following keymaps:

    - ``keymap`` - keys are raw python objects
    - ``hashmap`` - keys are a hash for the python object
    - ``stringmap`` - keys are the python object cast as a string
    - ``picklemap`` - keys are the serialized python object

``klepto`` also includes a few useful decorators providing:

    - simple, shallow, or deep rounding of function arguments
    - cryptographic key generation, with masking of selected arguments


Current Release
===============

This documentation is for version ``klepto-0.1.5.1``.

The latest released version of ``klepto`` is available from:

    https://pypi.org/project/klepto

``klepto`` is distributed under a 3-clause BSD license.

    >>> import klepto
    >>> print (klepto.license())


Development Version 
===================

You can get the latest development version with all the shiny new features at:

    https://github.com/uqfoundation

If you have a new contribution, please submit a pull request.


Installation
============

``klepto`` is packaged to install from source, so you must
download the tarball, unzip, and run the installer::

    [download]
    $ tar -xvzf klepto-0.1.5.1.tar.gz
    $ cd klepto-0.1.5.1
    $ python setup py build
    $ python setup py install

You will be warned of any missing dependencies and/or settings
after you run the "build" step above. 

Alternately, ``klepto`` can be installed with ``pip`` or ``easy_install``::

    $ pip install klepto


Requirements
============

``klepto`` requires:

    - ``python``, **version >= 2.5** or **version >= 3.1**, or ``pypy``
    - ``dill``, **version >= 0.2.8.1**
    - ``pox``, **version >= 0.2.4**

Optional requirements:

    - ``sqlalchemy``, **version >= 0.8.4**
    - ``setuptools``, **version >= 0.6**


More Information
================

Probably the best way to get started is to look at the documentation at
http://klepto.rtfd.io. Also see ``klepto.tests`` for a set of scripts that
test the caching and archiving functionalities in ``klepto``.
You can run the test suite with ``python -m klepto.tests``.  The
source code is also generally well documented, so further questions may
be resolved by inspecting the code itself. Please feel free to submit
a ticket on github, or ask a question on stackoverflow (**@Mike McKerns**).
If you would like to share how you use ``klepto`` in your work, please send
an email (to **mmckerns at uqfoundation dot org**).


Citation
========

If you use ``klepto`` to do research that leads to publication, we ask that you
acknowledge use of ``klepto`` by citing the following in your publication::

    Michael McKerns and Michael Aivazis,
    "pathos: a framework for heterogeneous computing", 2010- ;
    http://trac.mystic.cacr.caltech.edu/project/pathos

Please see http://trac.mystic.cacr.caltech.edu/project/pathos for
further information.

