构建器(Builder)模式是一种独特的设计模式，它有助于使用简单对象构建复杂对象并使用算法。 这种设计模式属于创建型模式。 在这种设计模式中，构建器类逐步构建最终对象。 该构建器独立于其他对象。

构建器(Builder)模式的优点

• 它提供了清晰的分离和独特的层次，可以在构建和表示由类创建的指定对象之间进行表示。
• 它可以更好地控制所建模式的实现过程。
• 它提供了改变对象内部表示的场景。

如何实现构建器模式？

在本节中，我们将学习如何实现构建器模式。参考以下实现代码 -

class Director:
   __builder = None

   def setBuilder(self, builder):
      self.__builder = builder

   def getCar(self):
      car = Car()

      # First goes the body
      body = self.__builder.getBody()
      car.setBody(body)

      # Then engine
      engine = self.__builder.getEngine()
      car.setEngine(engine)

      # And four wheels
      i = 0
      while i < 4:
         wheel = self.__builder.getWheel()
            car.attachWheel(wheel)
         i += 1
      return car

# The whole product
class Car:
   def __init__(self):
      self.__wheels = list()
      self.__engine = None
      self.__body = None

   def setBody(self, body):
      self.__body = body

   def attachWheel(self, wheel):
      self.__wheels.append(wheel)

   def setEngine(self, engine):
      self.__engine = engine

   def specification(self):
      print "body: %s" % self.__body.shape
      print "engine horsepower: %d" % self.__engine.horsepower
      print "tire size: %d\'" % self.__wheels[0].size

class Builder:
      def getWheel(self): pass
      def getEngine(self): pass
      def getBody(self): pass

class JeepBuilder(Builder):

   def getWheel(self):
      wheel = Wheel()
      wheel.size = 22
      return wheel

   def getEngine(self):
      engine = Engine()
      engine.horsepower = 400
      return engine

   def getBody(self):
      body = Body()
      body.shape = "SUV"
      return body

# Car parts
class Wheel:
   size = None

class Engine:
   horsepower = None

class Body:
   shape = None

def main():
   jeepBuilder = JeepBuilder() # initializing the class

   director = Director()

   # Build Jeep
   print "Jeep"
   director.setBuilder(jeepBuilder)
   jeep = director.getCar()
   jeep.specification()
   print ""

if __name__ == "__main__":
   main()

执行上面程序，得到以下输出结果 -