Source Code for Module pypat.structural.flyweight

 1 -class FlyweightMeta(type): 
 2      """ 
 3      Flyweight meta class as part of the Flyweight design pattern. 
 4   
 5      - External Usage Documentation: U{https://github.com/tylerlaberge/PyPatterns/wiki/Structural-Pattern-Usage} 
 6      - External Flyweight Pattern documentation: U{https://en.wikipedia.org/wiki/Flyweight_pattern} 
 7      """ 
 8 -    def __new__(mcs, name, bases, attrs): 
 9          """ 
10          Override class construction to add 'pool' attribute to classes dict. 
11   
12          @param name: The name of the class. 
13          @param bases: Base classes of the class. 
14          @param attrs: Attributes of the class. 
15          @return: A new Class. 
16          """ 
17          attrs['pool'] = dict() 
18          return super(FlyweightMeta, mcs).__new__(mcs, name, bases, attrs) 
19   
20      @staticmethod 
21 -    def _serialize(cls, *args, **kwargs): 
22          """ 
23          Serialize arguments to a string representation. 
24          """ 
25          serialized_args = [str(arg) for arg in args] 
26          serialized_kwargs = [str(kwargs), cls.__name__] 
27   
28          serialized_args.extend(serialized_kwargs) 
29   
30          return ''.join(serialized_args) 
31   
32 -    def __call__(cls, *args, **kwargs): 
33          """ 
34          Override call to use objects from a pool if identical parameters are used for object creation. 
35   
36          @param args: Arguments for class instantiation. 
37          @param kwargs: Keyword arguments for class instantiation. 
38          @return: A new instance of the class. 
39          """ 
40          key = FlyweightMeta._serialize(cls, *args, **kwargs) 
41          pool = getattr(cls, 'pool', {}) 
42   
43          instance = pool.get(key) 
44          if not instance: 
45              instance = super(FlyweightMeta, cls).__call__(*args, **kwargs) 
46              pool[key] = instance 
47   
48          return instance 
49