Perfect........
I think this can be added to the relevant section of the book, I
didn't find anything about that, also on the internet...
Thanks a lot, though.
Niphlod
On 8 Set, 03:08, mdipierro <mdipie...@cs.depaul.edu> wrote:
> Sorry for the lat reply. This is not a bug. This is a design issue and
> tradeoff.
>
> In fact there is a single virtualfields instance, the one you create
> in:
>
> db.test.virtualfields.append(TestLazy())
>
> and not one instance per record. There are two reasons for this:
> 1) allows cumulative virtualfields (values that depends on previous
> records)
> 2) save memory
>
> You can replace your code
>
> class TestLazy:
> def lazy_test_field(self):
> def lazy(self=self):
> return self.test.name
> return lazy
>
> with
>
> class TestLazy:
> def lazy_test_field(self):
> from copy import copy
> def lazy(self=copy(self)):
> return self.test.name
> return lazy
>
> and this would work as you expect. It is just that DAL leaves to you
> the responsibility of making the copy and using the extra memory and
> does not do it automatically because most of the cases it would be a
> waste.
>
> Massimo
>
> On Aug 21, 6:22 pm, Niphlod <niph...@gmail.com> wrote:
>
>
>
> > so, I read the docs and.....
>
> > I think either there's a bug or I'm doing something wrong....
>
> > in db.py
>
> > ---------------
> > .....
>
> > db.define_table('test',
> > Field('name', length=5)
> > )
>
> > class TestLazy:
> > def lazy_test_field(self):
> > deflazy(self=self):
> > return self.test.name
> > returnlazy
>
> > class TestNotLazy:
> > def not_lazy_test_field(self):
> > return self.test.name
>
> > db.test.virtualfields.append(TestLazy())
> > db.test.virtualfields.append(TestNotLazy())
>
> > ----------------
>
> > Testing in the shell
>
> > web2py Shell Version 1.83.2 (2010-08-15 08:16:30)
> > In[0]: set = db(db.test.id>0).select()
>
> > Out[0]:
> > In[1]: set.as_dict()
>
> > Out[1]: {1: {'name': 'miao', 'id': 1, 'not_lazy_test_field': 'miao'},
> > 2: {'name': 'bau', 'id': 2, 'not_lazy_test_field': 'bau'}}
>
> > In[2]:for row in set:
> > print row.id, row.name, row.not_lazy_test_field
>
> > Out[2]:
> > 1 miao miao
> > 2 bau bau
>
> > In[3]:
> > for row in set:
> > print row.id, row.name, row.not_lazy_test_field,
> > row.lazy_test_field
>
> > Out[3]:
> > 1 miao miao <functionlazyat 0x2e5c2a8>
> > 2 bau bau <functionlazyat 0x308ec80>
>
> > In[4]:
> > for row in set:
> > print row.id, row.name, row.not_lazy_test_field,
> > row.lazy_test_field()
>
> > Out[4]:
> > 1 miao miao bau
> > 2 bau bau bau
>
> > sorry for the unmeaning data in the set, but...seems thatlazy
> > virtualfield is evaluated every line (different hash function when you
> > try to print row.lazy_test_field without parenthesis, In[3]) but it
> > returns data computed for the last line in the set...in all the rows
> > of the set itself (In[4])
>
> > Can somebody point me in the right direction ?
> > Thanks- Nascondi testo citato
>
> - Mostra testo citato -
