Re: models, peeking to next record - maybe

[Tim Chase]

On 2015-02-07 22:05, Vijay Khemlani wrote:
> The direct solution would be something like this in your view
> 
> events = Event.objects.order_by('event_date')
> 
> event_tuples = []
> last_date_seen = None
> 
> for event in events:
> if last_date_seen:
> date_difference = event.date - last_date_seen
> else:
> date_difference = None
> 
> event_tuples.push((event, date_difference))

In the past I've created something like this as a filter, which lets
it be fairly generic. I also make it a generator rather than keeping
them all around. Something like (I don't have the exact code on hand)

  from django import template
  register = template.base.Library()
  @register.filter(name="pairwise")
  def pairwise(iterable, final=True):
i = iter(iterable)
a = next(i)
for b in i:
  yield a, b
  a = b
if final:
  yield a, None

-tkc



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Re: models, peeking to next record - maybe

[Thomas Rega]

Alternatively use the 'latest()' method of the django ORM to figure
out which is the latest event:
https://docs.djangoproject.com/en/1.7/ref/models/querysets/#latest

2015-02-08 2:05 GMT+01:00 Vijay Khemlani :
> The direct solution would be something like this in your view
>
> events = Event.objects.order_by('event_date')
>
> event_tuples = []
> last_date_seen = None
>
> for event in events:
> if last_date_seen:
> date_difference = event.date - last_date_seen
> else:
> date_difference = None
>
> event_tuples.push((event, date_difference))
>
> (date_difference would be a timedelta object)
>
> On Sat, Feb 7, 2015 at 10:02 PM, Lachlan Musicman  wrote:
>>
>> My initial suggestion would be to utilise the "order by" option, and
>> order by date.
>>
>> Then, on each model have a find_next function and a until_next function.
>>
>> The first would work out which was the next event, the other the time.
>> They could be coupled, but keeping them separate means you can utilise
>> them later if you need to.
>>
>> cheers
>> L.
>> --
>> "This is a profound psychological violence here. How can one even
>> begin to speak of dignity in labor when one secretly feels one's job
>> should not exist?"
>>
>> On the Phenomenon of Bullshit Jobs, David Graeber
>> http://strikemag.org/bullshit-jobs/
>>
>>
>> On 8 February 2015 at 09:40, Richard Bowden  wrote:
>> > Got an problem that I am struggling to solve..
>> >
>> > I have:
>> >
>> > class Address(models.Model):
>> > name = models.CharField()
>> > event_date = models.DateTime()
>> >
>> >
>> > event1, 25/01/2015
>> > event2, 27/01/2015
>> > event3, 05/02/2015
>> >
>> > and so on…
>> >
>> > what I am trying to figure out is, how to calculate the days between
>> > each
>> > event.
>> >
>> > so event2, would be 2 days, event3 would be 9 days etc.
>> >
>> > want to end up with something like this that is passed to the template
>> > event1, 25/01/2015
>> > event2, 27/01/2015, 2
>> > event3, 05/02/2015, 9
>> >
>> >
>> > its the mechanics I am having trouble working out, my initial though was
>> > to
>> > have a def on the model that accepted a datetime object. Somehow in a
>> > loop i
>> > would get the diatomite from the next event and pass it in and calc days
>> > on
>> > self.event_date… cant think how to do it.
>> >
>> > has anyone else needed something like this? or am I thinking about it
>> > wrong..
>> >
>> > Thanks
>> >
>> > --
>> > You received this message because you are subscribed to the Google
>> > Groups
>> > "Django users" group.
>> > To unsubscribe from this group and stop receiving emails from it, send
>> > an
>> > email to django-users+unsubscr...@googlegroups.com.
>> > To post to this group, send email to django-users@googlegroups.com.
>> > Visit this group at http://groups.google.com/group/django-users.
>> > To view this discussion on the web visit
>> >
>> > https://groups.google.com/d/msgid/django-users/63b0691e-34b1-4634-bf29-640583f22bae%40googlegroups.com.
>> >
>> > For more options, visit https://groups.google.com/d/optout.
>>
>> --
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>> For more options, visit https://groups.google.com/d/optout.
>
>
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>
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Re: models, peeking to next record - maybe

[Vijay Khemlani]

The direct solution would be something like this in your view

events = Event.objects.order_by('event_date')

event_tuples = []
last_date_seen = None

for event in events:
if last_date_seen:
date_difference = event.date - last_date_seen
else:
date_difference = None

event_tuples.push((event, date_difference))

(date_difference would be a timedelta object)

On Sat, Feb 7, 2015 at 10:02 PM, Lachlan Musicman  wrote:

> My initial suggestion would be to utilise the "order by" option, and
> order by date.
>
> Then, on each model have a find_next function and a until_next function.
>
> The first would work out which was the next event, the other the time.
> They could be coupled, but keeping them separate means you can utilise
> them later if you need to.
>
> cheers
> L.
> --
> "This is a profound psychological violence here. How can one even
> begin to speak of dignity in labor when one secretly feels one's job
> should not exist?"
>
> On the Phenomenon of Bullshit Jobs, David Graeber
> http://strikemag.org/bullshit-jobs/
>
>
> On 8 February 2015 at 09:40, Richard Bowden  wrote:
> > Got an problem that I am struggling to solve..
> >
> > I have:
> >
> > class Address(models.Model):
> > name = models.CharField()
> > event_date = models.DateTime()
> >
> >
> > event1, 25/01/2015
> > event2, 27/01/2015
> > event3, 05/02/2015
> >
> > and so on…
> >
> > what I am trying to figure out is, how to calculate the days between each
> > event.
> >
> > so event2, would be 2 days, event3 would be 9 days etc.
> >
> > want to end up with something like this that is passed to the template
> > event1, 25/01/2015
> > event2, 27/01/2015, 2
> > event3, 05/02/2015, 9
> >
> >
> > its the mechanics I am having trouble working out, my initial though was
> to
> > have a def on the model that accepted a datetime object. Somehow in a
> loop i
> > would get the diatomite from the next event and pass it in and calc days
> on
> > self.event_date… cant think how to do it.
> >
> > has anyone else needed something like this? or am I thinking about it
> > wrong..
> >
> > Thanks
> >
> > --
> > You received this message because you are subscribed to the Google Groups
> > "Django users" group.
> > To unsubscribe from this group and stop receiving emails from it, send an
> > email to django-users+unsubscr...@googlegroups.com.
> > To post to this group, send email to django-users@googlegroups.com.
> > Visit this group at http://groups.google.com/group/django-users.
> > To view this discussion on the web visit
> >
> https://groups.google.com/d/msgid/django-users/63b0691e-34b1-4634-bf29-640583f22bae%40googlegroups.com
> .
> >
> > For more options, visit https://groups.google.com/d/optout.
>
> --
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>

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Re: models, peeking to next record - maybe

[Lachlan Musicman]

My initial suggestion would be to utilise the "order by" option, and
order by date.

Then, on each model have a find_next function and a until_next function.

The first would work out which was the next event, the other the time.
They could be coupled, but keeping them separate means you can utilise
them later if you need to.

cheers
L.
--
"This is a profound psychological violence here. How can one even
begin to speak of dignity in labor when one secretly feels one's job
should not exist?"

On the Phenomenon of Bullshit Jobs, David Graeber
http://strikemag.org/bullshit-jobs/


On 8 February 2015 at 09:40, Richard Bowden  wrote:
> Got an problem that I am struggling to solve..
>
> I have:
>
> class Address(models.Model):
> name = models.CharField()
> event_date = models.DateTime()
>
>
> event1, 25/01/2015
> event2, 27/01/2015
> event3, 05/02/2015
>
> and so on…
>
> what I am trying to figure out is, how to calculate the days between each
> event.
>
> so event2, would be 2 days, event3 would be 9 days etc.
>
> want to end up with something like this that is passed to the template
> event1, 25/01/2015
> event2, 27/01/2015, 2
> event3, 05/02/2015, 9
>
>
> its the mechanics I am having trouble working out, my initial though was to
> have a def on the model that accepted a datetime object. Somehow in a loop i
> would get the diatomite from the next event and pass it in and calc days on
> self.event_date… cant think how to do it.
>
> has anyone else needed something like this? or am I thinking about it
> wrong..
>
> Thanks
>
> --
> You received this message because you are subscribed to the Google Groups
> "Django users" group.
> To unsubscribe from this group and stop receiving emails from it, send an
> email to django-users+unsubscr...@googlegroups.com.
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> Visit this group at http://groups.google.com/group/django-users.
> To view this discussion on the web visit
> https://groups.google.com/d/msgid/django-users/63b0691e-34b1-4634-bf29-640583f22bae%40googlegroups.com.
>
> For more options, visit https://groups.google.com/d/optout.

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models, peeking to next record - maybe

[Richard Bowden]

Got an problem that I am struggling to solve..

I have:

class Address(models.Model):
name = models.CharField()
event_date = models.DateTime()


event1, 25/01/2015
event2, 27/01/2015
event3, 05/02/2015

and so on…

what I am trying to figure out is, how to calculate the days between each 
event.

so event2, would be 2 days, event3 would be 9 days etc.

want to end up with something like this that is passed to the template
event1, 25/01/2015
event2, 27/01/2015, 2
event3, 05/02/2015, 9


its the mechanics I am having trouble working out, my initial though was to 
have a def on the model that accepted a datetime object. Somehow in a loop 
i would get the diatomite from the next event and pass it in and calc days 
on self.event_date… cant think how to do it.

has anyone else needed something like this? or am I thinking about it 
wrong..

Thanks

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models, peeking to next record - maybe

[Richard Bowden]

I am working on a problem that I am trying to figure out, not having much 
luck so far...


I have a model, basic for this example:

class Event(models.Model):

name = models.Charfield(max_length=10)
event_date = models.DateTime()



I am trying to workout how I can calculate the number of days between each 
event, the query set would be orders by event_date

event1, 26/01/2015
event2, 29/01/2015
event3, 03/02/2015

so event 2 would be 3 days and event 3 would be 5 days and so on.

my idea was to have a model def that accepted a datetime from the previous 
record which would calc the days against the self.event_date

its the mechanics of peeking at the next / previous record in a 
queryset...i am struggling with, not sure how to proceed with this 
problem

has anyone seen this before, or am I thinking about wrong ?

Thanks




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