[Python] Factory pattern again

Mike Howarth a ?crit :
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

Mike Howarth a ?crit :
cannot work, since price is an instance attribute, not a class attribute.

What you want is:

item = factory('Item')
print item.price

HTH
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http://mail.python.org/mailman/listinfo/python-list

Mike Howarth a ?crit :
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

Mike Howarth wrote:
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

On Jul 27, 11:26 pm, Mike Howarth wrote:
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:
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cunheise at yahoo.com.cn wrote:
first you need find the bottleneck of your script db or function
if the bottleneck is db
1. which db do you use do you optimize the db from read
2. the sql you write do not use any index "maybe select code, type
from products where type = 'I' or type = 'S' will help" and you need
create index on type field maybe you need set limit 2000 to sql depend
on your requirement