instance cache

instance_cache.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-
#
# Copyright (c) 2012, lepture.com
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
#
#    * Redistributions of source code must retain the above copyright
#      notice, this list of conditions and the following disclaimer.
#    * Redistributions in binary form must reproduce the above
#      copyright notice, this list of conditions and the following
#      disclaimer in the documentation and/or other materials provided
#      with the distribution.
#    * Neither the name of the author nor the names of its contributors
#      may be used to endorse or promote products derived from this
#      software without specific prior written permission.
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# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
# HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.


_app_cache = {}


class InstanceCache(object):
    def clear(self):
        global _app_cache

        for key, value in _app_cache.iteritems():
            expiry = value[1]
            if expiry and time() > expiry:
                del _app_cache[key]

    def flush_all(self):
        global _app_cache

        _app_cache = {}

    def set(self, key, value, seconds):
        global _app_cache

        if seconds < 0:
            seconds = 0

        _app_cache[key] = (value, time() + seconds if seconds else 0)

    def get(self, key):
        global _app_cache

        value = _app_cache.get(key, None)
        if value:
            expiry = value[1]
            if expiry and time() > expiry:
                del _app_cache[key]
                return None
            else:
                return value[0]
        return None

    def delete(self, key):
        global _app_cache

        if key in _app_cache:
            del _app_cache[key]
        return None