Package horizons :: Package util :: Package python :: Module defaultweakkeydictionary
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Source Code for Module horizons.util.python.defaultweakkeydictionary

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 4  # This file is part of Unknown Horizons. 
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21   
22  """ 
23  DefaultWeakKeyDictionary - Works as a regular WeakKeyDictionary but supports default values. 
24  Note: Default feature works slightly different than collections.defaultdict 
25   
26  Usage: 
27   
28  >>> d = DefaultWeakKeyDictionary(lambda key: key*2) 
29  >>> d['foo'] = 4 
30  >>> print d['foo'] 
31  4 
32  >>> print d['bar'] 
33  'barbar' 
34  """ 
35  from weakref import WeakKeyDictionary 
36   
37   
38 -class DefaultWeakKeyDictionary(WeakKeyDictionary):
39 """ 40 WeakKeyDictionary with specified default value. 41 """
42 - def __init__(self, default_function):
43 WeakKeyDictionary.__init__(self) 44 assert default_function is not None, "Default function must be provided" 45 self.default_function = default_function
46
47 - def __getitem__(self, item):
48 if item not in self.items(): 49 return self.default_function(item) 50 return WeakKeyDictionary.__getitem__(self, item)
51