shinken/memoized.py

   1 #!/usr/bin/env python
   2 #Copyright (C) 2009-2010 :
   3 #    Gabes Jean, naparuba@gmail.com
   4 #    Gerhard Lausser, Gerhard.Lausser@consol.de
   5 #    Gregory Starck, g.starck@gmail.com
   6 #    Hartmut Goebel, h.goebel@goebel-consult.de
   7 #
   8 #This file is part of Shinken.
   9 #
  10 #Shinken is free software: you can redistribute it and/or modify
  11 #it under the terms of the GNU Affero General Public License as published by
  12 #the Free Software Foundation, either version 3 of the License, or
  13 #(at your option) any later version.
  14 #
  15 #Shinken is distributed in the hope that it will be useful,
  16 #but WITHOUT ANY WARRANTY; without even the implied warranty of
  17 #MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18 #GNU Affero General Public License for more details.
  19 #
  20 #You should have received a copy of the GNU Affero General Public License
  21 #along with Shinken.  If not, see <http://www.gnu.org/licenses/>.
  22
  23
  24 class memoized(object):
  25     """Decorator that caches a function's return value each time it is called.
  26     If called later with the same arguments, the cached value is returned, and
  27     not re-evaluated.
  28     """
  29     def __init__(self, func):
  30         self.func = func
  31         self.cache = {}
  32     def __call__(self, *args):
  33         try:
  34             return self.cache[args]
  35         except KeyError:
  36             self.cache[args] = value = self.func(*args)
  37             return value
  38         except TypeError:
  39             # uncachable -- for instance, passing a list as an argument.
  40             # Better to not cache than to blow up entirely.
  41             return self.func(*args)
  42     def __repr__(self):
  43         """Return the function's docstring."""
  44         return self.func.__doc__
  45
  46
  47
  48 #def memoized(function, limit=None):
  49 #    if isinstance(function, int):
  50 #        def memoize_wrapper(f):
  51 #            return memoized(f, function)
  52 #
  53 #        return memoize_wrapper
  54 #
  55 #    dict = {}
  56 #    list = []
  57 #    def memoize_wrapper(*args, **kwargs):
  58 #       key = cPickle.dumps((args, kwargs))
  59 #       try:
  60 #          list.append(list.pop(list.index(key)))
  61 #       except ValueError:
  62 #          dict[key] = function(*args, **kwargs)
  63 #          list.append(key)
  64 #          if limit is not None and len(list) > limit:
  65 #             del dict[list.pop(0)]
  66 #
  67 #       return dict[key]
  68
  69 #    memoize_wrapper._memoize_dict = dict
  70 #    memoize_wrapper._memoize_list = list
  71 #    memoize_wrapper._memoize_limit = limit
  72 #    memoize_wrapper._memoize_origfunc = function
  73 #    memoize_wrapper.func_name = function.func_name
  74 #    return memoize_wrapper
  75
  76
  77
  78 #@memoized
  79 #def fibonacci(n):
  80 #   "Return the nth fibonacci number."
  81 #   print n
  82 #   if n in (0, 1):
  83 #      return n
  84 #   val = fibonacci(n-1) + fibonacci(n-2)
  85 #   return val#
  86 #
  87 #fibonacci(5)
  88 #fibonacci(12)