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Caching decorator

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  1. from datetime import datetime, timedelta
  2. from copy import deepcopy
  3. from threading import RLock
  4.  
  5. def timed_cache(seconds=0, minutes=0, hours=0, days=0):
  6.  
  7.     time_delta = timedelta( seconds=seconds,
  8.                             minutes=minutes,
  9.                             hours=hours,
  10.                             days=days )
  11.  
  12.     def decorate(f):
  13.  
  14.         f._lock = RLock()
  15.         f._updates = {}
  16.         f._results = {}
  17.  
  18.         def do_cache(*args, **kwargs):
  19.  
  20.             lock = f._lock
  21.             lock.acquire()
  22.  
  23.             try:
  24.                 key = (args, tuple(sorted(kwargs.items(), key=lambda i:i[0])))
  25.  
  26.                 updates = f._updates
  27.                 results = f._results
  28.  
  29.                 t = datetime.now()
  30.                 updated = updates.get(key, t)
  31.  
  32.                 if key not in results or t-updated > time_delta:
  33.                     # Calculate
  34.                     updates[key] = t
  35.                     result = f(*args, **kwargs)
  36.                     results[key] = deepcopy(result)
  37.                     return result
  38.  
  39.                 else:
  40.                     # Cache
  41.                     return deepcopy(results[key])
  42.  
  43.             finally:
  44.                 lock.release()
  45.  
  46.         return do_cache
  47.  
  48.     return decorate

URL: http://www.willmcgugan.com/blog/tech/2007/10/14/timed-caching-decorator/

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