Creational Design Patterns in Python: The Builder

Builder.py

#### The product to contruct ####
class Product(object):
  
  def __init__(self, extra):
    self.extra = extra
  
  def do_somthing(self):
    print "Doing Something{0}!".format(self.extra)
    
#### The Builder for a type of product ####
class NormalBuilder(object):
  
  def build_product(self):
    return Product("")
    
#### The Builder for another type of product ####
class ExtraBuilder(object):
    
  def build_product(self):
    return Product(" Else")
    
#### The class using the builders to build and serve products ####
class Director(object):
  
  def set_builder(self, builder):
    self.builder = builder
    
  def get_product(self):
    return self.builder.build_product()
    
    
def main():
  director = Director()
  director.set_builder(ExtraBuilder)
  product = director.get_product()
  product.do_somthing()

if __name__ == "__main__":
  main()

This may not seem at first like a particularly useful pattern, especially to new programmers yet it is exactly the sort of pattern used when drawing ui's.

painter.set_pen(new_pen)

using middleware

app = require(express);
app.use(express.basicAuth('username', 'password'));