#3587: filter() and order_by()
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Reporter: [EMAIL PROTECTED] | Owner: adrian
Status: new | Component: Database wrapper
Version: 0.95 | Resolution:
Keywords: | Stage: Unreviewed
Has_patch: 0 | Needs_docs: 0
Needs_tests: 0 | Needs_better_patch: 0
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Comment (by Michael Radziej <[EMAIL PROTECTED]>):
Putting the code into braces brings better readability:
{{{
sqn = models.ForeignKey?(Squadron) enrollment_date =
models.DateField?(help_text="YYYY-MM-DD") date_of_birth =
models.DateField?(help_text="YYYY-MM-DD")
class Camp(models.Model):
name = models.CharField?(maxlength=40) min_training_level =
models.PositiveIntegerField?("Minimum training level", default=0) min_age
= models.FloatField?("Minimum age", max_digits=3, decimal_places=1,
default=0)
class Application(models.Model):
cadet = models.ForeignKey?(Cadet, edit_inline=models.STACKED,
num_extra_on_change=1, num_in_admin=1) year =
models.IntegerField?(maxlength=4, core=True, help_text="4-digit year",
validator_list=[year_validator]) camp = models.ForeignKey?(Camp,
core=True) training_level = models.PositiveIntegerField?("current training
level")
The only places I can find where I couldn't get filtering to work are
where I'm doing something that is probably too complex to do with SQL
(although I'm no SQL expert).
Here's the function I ended up with after trying to get it going with
filter() : def exception_age(request, year_filter):
"""Lists cadets that might not be the right age for the course they
applied for.""" this_june = date(int(year_filter), 6, 1) this_sept =
date(int(year_filter), 9, 1) apps =
list(Application.objects.filter(year=year_filter)) # filter out any that
are definitely the right age apps = [a for a in apps if
(a.cadet.age_on(this_june) <
float(a.camp.min_age)) or (a.cadet.ages_out() < this_sept)]
I don't have the filter() versions that I tried along the way, but it was
based on comparing the application.cadet.date_of_birth field.
This one involves comparing the values in two tables : def
exception_eligibility(request, year_filter):
"""Lists cadets not in the right level for the course they applied
for.""" apps = list(Application.objects.filter(year=year_filter)) # filter
out any that are in the right level apps = [a for a in apps if
a.training_level < a.camp.min_training_level] # Sort the list by squadron
number apps.sort(key=sqn_of_app); return
render_to_response('camps/exception_eligibility.html',
{'object_list' : apps,})
and this one requires doing a calculation on the difference between two
fields (cadet.date_of_birth and cadet.enrollment_date) : def
exception_enrollment(request, year_filter):
"""Lists cadets enrolled too young who've applied this year.""" apps =
list(Application.objects.filter(year=year_filter)) # filter out any that
joined old enough cdts = [a.cadet for a in apps if
a.cadet.age_at_enrollment() < 12] # Sort the list by squadron number
cdts.sort(key=sqn_of_cdt); return
render_to_response('camps/exception_enrollment.html',
{'object_list' : cdts,})
I do have examples of where order_by doesn't work. Here's one : def
wing(app):
return app.cadet.sqn.wing.name
def camp_csv(request, year_filter, object_id):
... app_list = list(camp.application_set.filter(year=year_filter)) # Sort
by wing app_list.sort(key=wing)
# app_list =
camp.application_set.filter(year=year_filter).order_by('camps_applicationc
adet.sqn.wing.name')
}}}
--
Ticket URL: <http://code.djangoproject.com/ticket/3587#comment:3>
Django Code <http://code.djangoproject.com/>
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