Thanks fantastic thank you
I was also able to do:
result = obj.task_set.aggregate(Count('id'))['id__count']
to get the a count of the tasks for quote
I don't suppose you know any good books regarding Python/Django that I
could buy to help me learn the syntax better?
Many thanks
On Jan 17, 10:15 pm, Daniel Roseman <dan...@roseman.org.uk> wrote:
> On Jan 17, 8:28 pm, pfwd <pfwdt...@googlemail.com> wrote:
>
>
>
>
>
> > Hi am very new to Django/Python and I need some help with a model
> > method
>
> > I have two tables Linked by a foreign key and their forms are embedded
> > in the admin interface.
> > One table is called Quote and one table is called Task. The task table
> > has a field called time_taken
> > In the Quote list I want to display the total amount of time to under
> > go all the tasks in each quote.
>
> > This is what I'm doing and its just displaying (None) in the list
>
> > class QuoteAdmin(admin.ModelAdmin):
> > fieldset = [
> > (None, {'fields': ['q_number']})
> > ]
> > inlines = [TaskInline]
>
> > list_display = ('q_number', 'total_time','created_date')
>
> > def total_time(self,queryset):
> > task_objs = self.Task.objects.all()
>
> > total_time = 'No time taken'
>
> > for record in task_objs:
> > total_time = total_time + record.time_taken
> > return total_time
>
> > I'm trying to get all the tasks for each quote by doing
> > self.Task.objects.all() and then looping through them and adding the
> > time_taken to the var total_time.
>
> > I guess this syntax is just plain wrong or the method is not being
> > called as its not showing any errors
> > I have a javascript/PHP background and I would like to learn more
> > Python
> > - Please be kind :)
>
> OK a few pointers.
>
> * a custom list_display method takes parameters (self, obj), where obj
> is the object being displayed in that row - here it's an instance of
> Quote.
> * 'self.Task' means nothing. You want to get the tasks related to the
> Quote, which is in 'obj', so you use 'obj.task_set.all()'. With this,
> your code would work as is.
> * A nicer way of doing it would be to get the DB to sum the time_taken
> values. This should work:
> from django.db.models import Sum
> return obj.task_set.aggregate(Sum('time_taken'))
> ['time_taken__sum']
> (the square brackets at the end are needed because 'aggregate' returns
> a dictionary, and we just want the value from there).
> --
> DR.
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