Implemented Flyweight design pattern.

pypatterns/structural/flyweight.py

@@ -0,0 +1,43 @@
+class FlyweightMeta(type):
+    """
+    Flyweight meta class as part of the Flyweight design pattern.
+    """
+    def __new__(mcs, name, bases, attrs):
+        """
+        Override class construction to add 'pool' attribute to classes dict.
+        @param name: The name of the class.
+        @param bases: Base classes of the class.
+        @param attrs: Attributes of the class.
+        @return: A new Class.
+        """
+        attrs['pool'] = dict()
+        return super(FlyweightMeta, mcs).__new__(mcs, name, bases, attrs)
+
+    @staticmethod
+    def _serialize_params(cls, *args, **kwargs):
+        """
+        Serialize input parameters to a key.
+        Simple implementation is just to serialize it as a string
+        """
+        args_list = [str(arg) for arg in args]
+        args_list.extend([str(kwargs), cls.__name__])
+        key = ''.join(args_list)
+        return key
+
+    def __call__(cls, *args, **kwargs):
+        """
+        Override call to use objects from a pool if identical parameters are used for object creation.
+
+        @param args: Arguments for class instantiation.
+        @param kwargs: Keyword arguments for class instantiation.
+        @return: A new instance of the class.
+        """
+        key = FlyweightMeta._serialize_params(cls, *args, **kwargs)
+        pool = getattr(cls, 'pool', {})
+
+        instance = pool.get(key)
+        if not instance:
+            instance = super(FlyweightMeta, cls).__call__(*args, **kwargs)
+            pool[key] = instance
+
+        return instance