add Flyweight pattern

Author: JakubVojvoda

flyweight/Flyweight.py

@@ -0,0 +1,67 @@
+#
+# Python Design Patterns: Flyweight
+# Author: Jakub Vojvoda [github.com/JakubVojvoda]
+# 2016
+#
+# Source code is licensed under MIT License
+# (for more details see LICENSE)
+# 
+
+import sys
+
+#
+# Flyweight
+# declares an interface through which flyweights can receive
+# and act on extrinsic state
+#
+class Flyweight:
+  def operation(self):
+    pass
+  
+#
+# UnsharedConcreteFlyweight
+# not all subclasses need to be shared
+#
+class UnsharedConcreteFlyweight(Flyweight):
+  def __init__(self, state):
+    Flyweight.__init__(self)
+    self._state = state
+  
+  def operation(self):
+    print("Unshared Flyweight with state " + str(self._state))
+
+#
+# ConcreteFlyweight
+# implements the Flyweight interface and adds storage
+# for intrinsic state
+#
+class ConcreteFlyweight(Flyweight):
+  def __init__(self, state):
+    Flyweight.__init__(self)
+    self._state = state
+    
+  def operation(self):
+    print("Concrete Flyweight with state " + str(self._state))
+
+#
+# FlyweightFactory
+# creates and manages flyweight objects and ensures
+# that flyweights are shared properly
+#
+class FlyweightFactory:
+  def __init__(self):
+    self._flies = {}
+  
+  def getFlyweight(self, key):
+    if (self._flies.get(key) is not None):
+      return self._flies.get(key)
+    
+    self._flies[key] = ConcreteFlyweight(key)        
+    return self._flies.get(key)
+
+
+if __name__ == "__main__":
+  factory = FlyweightFactory()
+
+  factory.getFlyweight(1).operation()
+  factory.getFlyweight(2).operation()