add Builder pattern

Author: JakubVojvoda

builder/Builder.py

@@ -0,0 +1,120 @@
+#
+# Python Design Patterns: Builder
+# Author: Jakub Vojvoda [github.com/JakubVojvoda]
+# 2016
+#
+# Source code is licensed under MIT License
+# (for more details see LICENSE)
+# 
+
+import sys
+
+#
+# Product
+# the final object that will be created using Builder
+#
+class Product:
+  def __init__(self):
+    self._partA = ""
+    self._partB = ""
+    self._partC = ""
+
+  def makeA(self, part):
+    self._partA = part
+        
+  def makeB(self, part):
+    self._partB = part
+  
+  def makeC(self, part):
+    self._partC = part
+  
+  def get(self):
+    return self._partA +" "+ self._partB +" "+ self._partC  
+
+#
+# Builder
+# abstract interface for creating products
+#
+class Builder:
+  def __init__(self):
+    self._product = Product()
+    
+  def get(self):
+    return self._product
+
+  def buildPartA():
+    pass
+    
+  def buildPartB():
+    pass
+  
+  def buildPartC():
+    pass
+
+#
+# Concrete Builders
+# create real products and stores them in the composite structure
+#
+class ConcreteBuilderX(Builder):
+  def __init__(self):
+    Builder.__init__(self)
+
+  def buildPartA(self):
+    self._product.makeA("A-X")
+  
+  def buildPartB(self):
+    self._product.makeB("B-X")
+  
+  def buildPartC(self):
+    self._product.makeC("C-X")    
+
+class ConcreteBuilderY(Builder):
+  def __init__(self):
+    Builder.__init__(self)
+  
+  def buildPartA(self):
+    self._product.makeA("A-Y")
+  
+  def buildPartB(self):
+    self._product.makeB("B-Y")
+  
+  def buildPartC(self):
+    self._product.makeC("C-Y")    
+
+#
+# Director
+# responsible for managing the correct sequence of object creation
+#
+class Director:
+  def __init__(self):
+    self._builder = None
+  
+  def set(self, builder):
+    self._builder = builder  
+
+  def get(self):
+    return self._builder.get()
+  
+  def construct(self):
+    self._builder.buildPartA()
+    self._builder.buildPartB()
+    self._builder.buildPartC()
+      
+
+if __name__ == "__main__":
+  builderX = ConcreteBuilderX()
+  builderY = ConcreteBuilderY()  
+  
+  director = Director()
+  director.set(builderX)  
+  director.construct()
+  
+  product1 = director.get()
+  print("1st product parts: " + product1.get())
+  
+  director.set(builderY)  
+  director.construct()
+  
+  product2 = director.get()
+  print("2nd product parts: " + product2.get())
+