Factory pattern again

Mike Howarth hey at mikehowarth.co.uk
Fri Jul 27 17:26:39 CEST 2007


Having overcome my first hurdle with the factory pattern, I've now hit
another stumbling block

At the moment I'm trying to return around 2000 records from a db and load up
the relevant product object, what I've found is this is running extremely
slowly (> 20mins), the db is normalized and indexes exist.

Can anyone advise on how best I could speed this up?

   def getWebRangeProducts(self):
        
        if self.c.connected:
                     
            cu = self.c.cursor #create the cursor
            
            sql = "SELECT type, code FROM products"
                            
            cu.execute(sql)
            
            if cu.rowcount > 0:
            
                rows = cu.fetchall()
    
                for row in rows: 
                    
                   self.loadProduct(row[0].strip(),row[1].strip())


                return self.products
            
            
    def loadProduct(self,type,product_code):
        
        print type + ":" + product_code
          
        if type == 'I':
            
            try:
                product = factory('Item', product_code)
                self.products.append(product)
            except:
                print 'problem occured:' + type + ':' + product_code
            
        elif type == 'S':
            
            try:
                item_set = factory('Set', product_code)
                item_set.getItems()
                self.products.extend(item_set.getItems())
            except:
                print 'problem occured:' + type + ':' + product_code

        else:
            pass







Bruno Desthuilliers-5 wrote:
> 
> Mike Howarth a écrit :
>> Hi 
>> 
>> I was wondering whether anyone could help me, I'm pretty new to python
>> coming from a PHP background and I'm having a few products in getting my
>> head round how to write the factory pattern within python.
>> 
>> I'm currently looking to try to return values from a db and load up the
>> relevant objects, values returned are product type (I,S) and product code
>> (123).
>> 
>> At the moment I've adapted some code I've found illustrating the factory
>> method but ideally I would like to use the type to load up the relevant
>> object.
>> 
>> Another issue I've found is that I don't seem to be able to access to the
>> price attribute of each of the object. I'm sure these are very
>> straightforward issues however I seem to have tied myself in knots over
>> this
>> and could do with a fresh set of 'pythonic' eyes to help me out.
>> 
>> registry = {}
>> 
>> class MetaBase(type):
>>      def __init__(cls, name, bases, dict):
>>          registry[name] = cls
>> 
>> class Product(object):
>>      __metaclass__ = MetaBase
>> 
>> class Item(Product):
>>      def __init__(self, *args, **kw): 
>>          self.price = 1
>>          
>> class Set(Product):
>>      def __init__(self, *args, **kw): 
>>          self.price = 2
>>          
>> def factory(kind, *args, **kw):
>>      return registry[kind](*args, **kw) 
>>  
>> 
>> item = registry['Item']
> 
> This returns the Item *class*, not an instance of... So the following:
> 
>> print item.price
> 
> cannot work, since price is an instance attribute, not a class attribute.
> 
> What you want is:
> 
> item = factory('Item')
> print item.price
> 
> HTH
> -- 
> http://mail.python.org/mailman/listinfo/python-list
> 
> 

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