Python dumbed down lru cache class

lru_cache.py

import logging

'''
THIS IS A WORK IN PROGRESS. Do not use unless you fully understand this
code, and can make needed modifications.
'''

class LRUCache(object):
    ''' Dumb/fake least recently used cache to just run in memory.
    '''
    def __init__(self, total_size=500):
        '''Pass the size in megabytes. We want provide a low ball estimation.
        '''
        self._objs = {}
        self.lru_queue = []
        self.bytes_free = total_size * 1000000.0
        self.total_size = total_size *       1000000.0

    def __contains__(self, item):
        'So you can do "my_key in lru"'
        return item in self._objs

    def info(self):
        return {'used_megs': "%.4f" %( (self.total_size - self.bytes_free) / 1000000.0 ),
                'remaining_megs': "%.4f"%( (self.bytes_free / 1000000.0) )}

    def add(self, name, obj, bytes_estimation):
        assert bytes_estimation <= self.total_size,\
        "The LRU cache cannot exceed %i" % self.total_size
        if name in self._objs:
            logging.warn("[LRUCache] (%s) was already in cache", name)
            return

        while self.bytes_free < bytes_estimation:
            logging.warn("[LRUCache] Only have (%i) bytes free, need (%i), popping an item", self.bytes_free, bytes_estimation)
            self._del_first_item()

        logging.warn("[LRUCache] Adding object of name (%s) with estimated bytes (%i)", name, bytes_estimation)
        self._objs[name] = {'name': name, 'bytes_estimation': bytes_estimation, 'obj': obj}
        self.lru_queue.append(name)
        self.bytes_free -= bytes_estimation
        logging.warn("[LRUCache] Is now holding (%i) bytes", self.total_size - self.bytes_free)

    def get(self, name):
        if name in self._objs:
            return self._objs[name]['obj']

    def _del_first_item(self):
        # Pop first item
        i = self.lru_queue.pop(0)
        logging.warn("[LRUCache] Removing (%s) from the cache", i)
        self.bytes_free += self._objs[i]['bytes_estimation']
        del self._objs[i]