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 18  """Dictionary with item expiration.""" 
 19   
 20  __revision__="$Id: expdict.py 600 2005-08-19 10:45:03Z jajcus $" 
 21  __docformat__="restructuredtext en" 
 22   
 23  import time 
 24  import threading 
 25   
 27      """An extension to standard Python dictionary objects which implements item 
 28      expiration. 
 29   
 30      Each item in ExpiringDictionary has its expiration time assigned, after 
 31      which the item is removed from the mapping. 
 32   
 33      :Ivariables: 
 34          - `_timeouts`: a dictionary with timeout values and timeout callback for 
 35            stored objects. 
 36          - `_default_timeout`: the default timeout value (in seconds from now). 
 37          - `_lock`: access synchronization lock. 
 38      :Types: 
 39          - `_timeouts`: `dict` 
 40          - `_default_timeout`: `int` 
 41          - `_lock`: `threading.RLock`""" 
 42   
 43      __slots__=['_timeouts','_default_timeout','_lock'] 
 44   
 46          """Initialize an `ExpiringDictionary` object. 
 47   
 48          :Parameters: 
 49              - `default_timeout`: default timeout value for stored objects. 
 50          :Types: 
 51              - `default_timeout`: `int`""" 
 52          dict.__init__(self) 
 53          self._timeouts={} 
 54          self._default_timeout=default_timeout 
 55          self._lock=threading.RLock() 
  56   
 64   
 72   
 75   
 76 -    def set_item(self,key,value,timeout=None,timeout_callback=None): 
  77          """Set item of the dictionary. 
 78   
 79          :Parameters: 
 80              - `key`: the key. 
 81              - `value`: the object to store. 
 82              - `timeout`: timeout value for the object (in seconds from now). 
 83              - `timeout_callback`: function to be called when the item expires. 
 84                The callback should accept none, one (the key) or two (the key 
 85                and the value) arguments. 
 86          :Types: 
 87              - `key`: any hashable value 
 88              - `value`: any python object 
 89              - `timeout`: `int` 
 90              - `timeout_callback`: callable""" 
 91          self._lock.acquire() 
 92          try: 
 93              if not timeout: 
 94                  timeout=self._default_timeout 
 95              self._timeouts[key]=(time.time()+timeout,timeout_callback) 
 96              return dict.__setitem__(self,key,value) 
 97          finally: 
 98              self._lock.release() 
  99   
101          """Do the expiration of dictionary items. 
102   
103          Remove items that expired by now from the dictionary.""" 
104          self._lock.acquire() 
105          try: 
106              for k in self._timeouts.keys(): 
107                  self._expire_item(k) 
108          finally: 
109              self._lock.release() 
 110   
112          """Do the expiration of a dictionary item. 
113   
114          Remove the item if it has expired by now. 
115   
116          :Parameters: 
117              - `key`: key to the object. 
118          :Types: 
119              - `key`: any hashable value""" 
120          (timeout,callback)=self._timeouts[key] 
121          if timeout<=time.time(): 
122              if callback: 
123                  try: 
124                      callback(key,dict.__getitem__(self,key)) 
125                  except TypeError: 
126                      try: 
127                          callback(key) 
128                      except TypeError: 
129                          callback() 
130              del self[key] 
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