In article <513d18d6$0$6512$c3e8da3$54964...@news.astraweb.com>,
Steven D'Aprano wrote:
> On Sun, 10 Mar 2013 18:34:58 -0400, Roy Smith wrote:
>
> > Yeah, that's what I was afraid of. The "obvious" solution of:
> >
> > class QuerySet(mongoengine.queryset.QuerySet):
> > def __init__(self,
On Sun, 10 Mar 2013 18:34:58 -0400, Roy Smith wrote:
> Yeah, that's what I was afraid of. The "obvious" solution of:
>
> class QuerySet(mongoengine.queryset.QuerySet):
> def __init__(self, document, collection):
> super(QuerySet, self).__init__(document, collection) [...]
> d
In article ,
Terry Reedy wrote:
> > It turns out, we don't actually use QuerySet in our models. We've
> > defined our own QuerySet subclass which adds a few convenience methods.
> > Adding
> >
> > def __len__(self):
> > raise NotImplemented
> >
> > to our subclass should do the jo
On 3/10/2013 9:05 AM, Roy Smith wrote:
In article ,
Roy Smith wrote:
The problem is, QuerySets have a __len__() method. Calling it is a lot
faster than iterating over the whole query set and counting the items,
but it does result in an additional database query, which is a lot
slower than t
In article ,
Roy Smith wrote:
> The problem is, QuerySets have a __len__() method. Calling it is a lot
> faster than iterating over the whole query set and counting the items,
> but it does result in an additional database query, which is a lot
> slower than the list resizing! Writing the c
In article <513a26fa$0$30001$c3e8da3$54964...@news.astraweb.com>,
Steven D'Aprano wrote:
> On Wed, 06 Mar 2013 22:20:11 -0500, Roy Smith wrote:
>
> > I stumbled upon an interesting bit of trivia concerning lists and list
> > comprehensions today.
> >
> > We use mongoengine as a database model
On Wed, 06 Mar 2013 22:20:11 -0500, Roy Smith wrote:
> I stumbled upon an interesting bit of trivia concerning lists and list
> comprehensions today.
>
> We use mongoengine as a database model layer. A mongoengine query
> returns an iterable object called a QuerySet. The "obvious" way to
> crea
On 3/7/2013 3:41 PM, Wolfgang Maier wrote:
Iterators do not generally have __len__ methods.
len(iter(range(10)))
Traceback (most recent call last):
File "", line 1, in
TypeError: object of type 'range_iterator' has no len()
But iterators have a length hint method that are used for some
> >>> Iterators do not generally have __len__ methods.
> >>>
> >>> >>> len(iter(range(10)))
> >>> Traceback (most recent call last):
> >>> File "", line 1, in
> >>> TypeError: object of type 'range_iterator' has no len()
> >>
> >> But iterators have a length hint method that are used for some
>
On 3/7/2013 11:20 AM, Christian Heimes wrote:
But iterators have a length hint method that are used for some
optimizations and preallocations, too.
This is easy when the base iterable has a length method, as do range
objects.
i = iter(range(10))
i.__length_hint__()
10
And the length_hin
On 3/7/2013 11:00 AM, Ian Kelly wrote:
But on this point, you are correct. The mongoengine QuerySet.__iter__
method is defined as:
def __iter__(self):
self.rewind()
return self
This is unfortunate design. Not only does it mean that the iterator's
__len__ method cannot
On Thu, Mar 7, 2013 at 12:19 PM, Stefan Behnel wrote:
>> Didn't know about that, thanks. Presumably a proper iter(QuerySet())
>> object could implement __length_hint__ in an efficient manner rather
>> than by just calling the __len__ of the underlying QuerySet,
>
> And how exactly would it do tha
Ian Kelly, 07.03.2013 18:31:
> On Thu, Mar 7, 2013 at 9:20 AM, Christian Heimes wrote:
>> Am 07.03.2013 17:00, schrieb Ian Kelly:
>>> On Thu, Mar 7, 2013 at 4:22 AM, Wolfgang Maier wrote:
Well, it skips the costly len() call because your iter(Foo()) returns
iter(range()) under the hood an
On Thu, Mar 7, 2013 at 9:20 AM, Christian Heimes wrote:
> Am 07.03.2013 17:00, schrieb Ian Kelly:
>> On Thu, Mar 7, 2013 at 4:22 AM, Wolfgang Maier
>> wrote:
>>> Well, it skips the costly len() call because your iter(Foo()) returns
>>> iter(range()) under the hood and list() uses that object's __
Am 07.03.2013 17:00, schrieb Ian Kelly:
> On Thu, Mar 7, 2013 at 4:22 AM, Wolfgang Maier
> wrote:
>> Well, it skips the costly len() call because your iter(Foo()) returns
>> iter(range()) under the hood and list() uses that object's __len__() method.
>
> Iterators do not generally have __len__ me
On Thu, Mar 7, 2013 at 4:22 AM, Wolfgang Maier
wrote:
> Well, it skips the costly len() call because your iter(Foo()) returns
> iter(range()) under the hood and list() uses that object's __len__() method.
Iterators do not generally have __len__ methods.
>>> len(iter(range(10)))
Traceback (most r
Tim Chase tim.thechases.com> writes:
> On 2013-03-06 22:20, Roy Smith wrote:
> > I stumbled upon an interesting bit of trivia concerning lists and
> > list comprehensions today.
>
> A little testing
> shows that this can be rewritten as
>
> my_objects = list(iter(my_query_set))
>
> which se
Roy Smith wrote:
> I stumbled upon an interesting bit of trivia concerning lists and list
> comprehensions today.
>
> We use mongoengine as a database model layer. A mongoengine query
> returns an iterable object called a QuerySet. The "obvious" way to
> create a list of the query results would
On 2013-03-06 22:20, Roy Smith wrote:
> I stumbled upon an interesting bit of trivia concerning lists and
> list comprehensions today.
I agree with Dave Angel that this is interesting. A little testing
shows that this can be rewritten as
my_objects = list(iter(my_query_set))
which seems to th
On 03/06/2013 10:20 PM, Roy Smith wrote:
I stumbled upon an interesting bit of trivia concerning lists and list
comprehensions today.
We use mongoengine as a database model layer. A mongoengine query
returns an iterable object called a QuerySet. The "obvious" way to
create a list of the query
I stumbled upon an interesting bit of trivia concerning lists and list
comprehensions today.
We use mongoengine as a database model layer. A mongoengine query
returns an iterable object called a QuerySet. The "obvious" way to
create a list of the query results would be:
my_objects = list
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