memory_pickle backend for dogpile.cache

memory_pickle.py

"""
Memory Backend
--------------

Provides a simple dictionary-based backend.

"""

from dogpile.cache.api import CacheBackend, NO_VALUE

try:
    import cPickle as pickle
except ImportError:
    import pickle

class MemoryPickleBackend(CacheBackend):
    """A backend that uses a plain dictionary , but serializes and deserializes 
    the objects.  This is done to achieve parity with other cache backends
    where returned values are not the same object.

    There is no size management, and values which
    are placed into the dictionary will remain
    until explicitly removed.   Note that
    Dogpile's expiration of items is based on
    timestamps and does not remove them from
    the cache.

    E.g.::

        from dogpile.cache import make_region

        region = make_region().configure(
            'dogpile.cache.memory'
        )


    To use a Python dictionary of your choosing,
    it can be passed in with the ``cache_dict``
    argument::

        my_dictionary = {}
        region = make_region().configure(
            'dogpile.cache.memory',
            arguments={
                "cache_dict":my_dictionary
            }
        )


    """
    def __init__(self, arguments):
        self._cache = arguments.pop("cache_dict", {})

    def get(self, key):
        value = self._cache.get(key, NO_VALUE)
        if value is not NO_VALUE:
            value = pickle.loads( value )
        return value 

    def get_multi(self, keys):
        values = []
        for key in keys :
            values.append( self.get( key ) )
        return values

    def set(self, key, value):
        pickled = pickle.dumps( value )
        self._cache[key] = pickled

    def set_multi(self, mapping):
        for key,value in mapping.items():
            pickled = pickle.dumps( value )
            self._cache[key] = pickled

    def delete(self, key):
        self._cache.pop(key, None)

    def delete_multi(self, keys):
        for key in keys:
            self._cache.pop(key, None)