I am passing several values to a view through my url. Through some blind luck (read experienced debugging (: ) I fixed an issue I had where the view was interpreting the arguments in an unexpected fashion. The old url looked like:
url(r'^explore/(?P<id>[\w\-]+)-(?P<region>[\w\-]+)-(?P<location_name>[-\w]+)-(?P<page>[\w\-]+)/$',
'project.apps.web_feed.views.display_feed', name='display_feed'),
My display_feed view looked like this:
def display_feed(request, id, region, location_name, page):
url_scheme = id + '-' + region + '-' + location_name
print location_name
There are several instances where the value for location_name was two words and the url that was called would look like this:
/explore/90-LA-Los-Angeles-0/
In my display_feed view, the value of location_name would be:
Angeles
This caused obvious problems when trying to query data and display it on the page.
When I rearranged the order of the url to have location_name as the first value like so:
url(r'^explore/(?P<location_name>[-\w]+)-(?P<id>[\w\-]+)-(?P<region>[\w\-]+)-(?P<page>[\w\-]+)/$',
'heylets.apps.web_feed.views.display_search_feed', name='search_feed'),
and updated the view to correspond with the above changes, the logic works swimmingly and the data displays on the page as expected.
I assume there are issues with the structure of the url, but I don't want to chalk this up to inexperience and move on without first understanding what I was doing wrong.
I think the issue is you were putting a ton of info in the same place without a clear delimiter. You were separating your values with a "-", but in the case of a multi-word name you were using "-" as a separator too, which can lead to unexpected results. If you are going to keep the same structure, separate your multi-word names with "_" or something different.
There may be better approaches, like the one points out: querystring.
You can get them on a dict and use them later, and you won't have that issue.
Another approach could be to separate your args with a different char, so your urls look like "/explore/90/LA/Los-Angeles/0/". This is the way it is shown in django tutorials and way cleaner than your approach.
Related
I have this query:
checkins = CheckinAct.objects.filter(time__range=[start, end], location=checkin.location)
Which works great for telling me how many checkins have happened in my date range for a specific location. But I want know how many checkins were done by unique users. So I tried this:
checkins = CheckinAct.objects.filter(time__range=[start, end], location=checkin.location).values('user').distinct()
But that doesn't work, I get back an empty Array. Any ideas why?
Here is my CheckinAct model:
class CheckinAct(models.Model):
user = models.ForeignKey(User)
location = models.ForeignKey(Location)
time = models.DateTimeField()
----Update------
So now I have updated my query to look like this:
checkins = CheckinAct.objects.values('user').\
filter(time__range=[start, end], location=checkin.location).\
annotate(dcount=Count('user'))
But I'm still getting multiple objects back that have the same user, like so:
[{'user': 15521L}, {'user': 15521L}, {'user': 15521L}, {'user': 15521L}, {'user': 15521L}]
---- Update 2------
Here is something else I tried, but I'm still getting lots of identical user objects back when I log the checkins object.
checkins = CheckinAct.objects.filter(
time__range=[start, end],
location=checkin.location,
).annotate(dcount=Count('user')).values('user', 'dcount')
logger.info("checkins!!! : " + str(checkins))
Logs the following:
checkins!!! : [{'user': 15521L}, {'user': 15521L}, {'user': 15521L}]
Notice how there are 3 instances of the same user object. Is this working correctly or not? Is there a difference way to read out what comes back in the dict object? I just need to know how many unique users check into that specific location during the time range.
The answer is actually right in the Django docs. Unfortunately, very little attention is drawn to the importance of the particular part you need; so it's understandably missed. (Read down a little to the part dealing with Items.)
For your use-case, the following should give you exactly what you want:
checkins = CheckinAct.objects.filter(time__range=[start,end], location=checkin.location).\
values('user').annotate(checkin_count=Count('pk')).order_by()
UPDATE
Based on your comment, I think the issue of what you wanted to achieve has been confused all along. What the query above gives you is a list of the number of times each user checked in at a location, without duplicate users in said list. It now seems what you really wanted was the number of unique users that checked in at one particular location. To get that, use the following (which is much simpler anyways):
User.objects.filter(checkinat__location=location).distinct().count()
UPDATE for non-rel support
checkin_users = [(c.user.pk, c.user) for c in CheckinAct.objects.filter(location=location)]
unique_checkins = len(dict(checkin_users))
This works off the principle that dicts have unique keys. So when you convert the list of tuples to a dict, you end up with a list of unique users. But, this will generate 1*N queries, where N is the total amount of checkins (one query each time the user attribute is used. Normally, I'd do something like .select_related('user'), but that too requires a JOIN, which is apparently out. JOINs not being supported seems like a huge downside to non-rel, if true, but if that's the case this is going to be your only option.
You don't want DISTINCT. You actually want Django to do something that will end up giving you a GROUP BY clause. You are also correct that your final solution is to combine annotate() and values(), as discussed in the Django documentation.
What you want to do to get your results is to use annotate first, and then values, such as:
CheckinAct.objects.filter(
time__range=[start, end],
location=checkin.location,
).annotate(dcount=Count('user').values('user', 'dcount')
The Django docs at the link I gave you above show a similarly constructed query (minus the filter aspect, which I added for your case in the proper location), and note that this will "now yield one unique result for each [checkin act]; however, only the [user] and the [dcount] annotation will be returned in the output data". (I edited the sentence to fit your case, but the principle is the same).
Hope that helps!
checkins = CheckinAct.objects.values('user').\
filter(time__range=[start, end], location=checkin.location).\
annotate(dcount=Count('user'))
If I am not mistaken, wouldn't the value you want be in the input as "dcount"? As a result, isn't that just being discarded when you decide to output the user value alone?
Can you tell me what happens when you try this?
checkins = CheckinAct.objects.values('user').\
filter(time__range=[start, end], location=checkin.location).\
annotate(Count('user')).order_by()
(The last order_by is to clear any built-in ordering that you may already have at the model level - not sure if you have anything like that, but doesn't hurt to ask...)
My lack of CS and inexperience is really coming to the forefront in this moment. I've never really handled filtering results server side. I'm thinking that this is not the right way to go about it. I'm using Django....
First, I assume that I can keep it DRYer by keeping this validation in my form definitions. Next, I was concerned about my chained filter statements. How important is it to use Q complex lookups as opposed to chaining filters at this point? I'm just building a prototype and I assume that I'll eventually have to go for a search solution more powerful than full text search.
My big issue right now (besides the length of the code and clearly the inefficiency) is that I'm not sure how to handle my rooms and workers inputs, which are select forms. If the user does not select a value, I want to remove these filters from the process server side. Should I just create two separate conditional series of lookups for these outcomes?
def search(request):
if request.method=='GET' and request.GET.get('region',''):
neighborhoods=request.GET.getlist('region')
min_rent=request.GET.get('min_cost','0')
min_rent=re.sub(r'[,]','',min_cost) #remove any ','
if re.search(r'[^\d]',min_cost):
min_cost=0
else:
min_cost=int(min_cost)
max_cost=request.GET.get('max_cost','0')
max_cost=re.sub(r'[,]','',max_cost) #remove any ','
if re.search(r'[^\d]',max_cost):
max_cost=100000
else:
max_cost=int(max_rent)
date_min=request.GET.get('from','')
date_max=request.GET.get('to','')
if not date_min:
date=(str(datetime.date.today()))
date_min=u'%s' %date
if not date_max:
date_max=u'2013-03-18'
rooms=request.GET.get('rooms',0)
if not rooms:
rooms=0
workers=request.GET.get('workers',0)
if not workers:
workers=0
#I should probably use Q objects here for complex lookups
posts=Post.objects.filter(region__in=region).filter(cost__gt=min_cost).filter(cost__lt=max_cost).filter(availability__gt=date_min).filter(availability__lt=date_max).filter(rooms=rooms).filter(workers=workers)
#return HttpResponse('%s' %posts)
return render_to_response("website/search.html",{'posts':posts),context_instance=RequestContext(request))
First, I assume that I can keep it
DRYer by keeping this validation in my
form definitions.
Yes, I'd put this in a form as it looks like you are using one to display the form anyways? Also, you can put a lot of your date formatting stuff right in the clean_FIELD methods to format the data in the cleaned_data dict. The only issue here is that output is actually modified so your users will see the change from 1,000 to 1000. Either way, I would put this logic in a form method.
# makes the view clean.
if form.is_valid():
form.get_posts(request)
return response
My big issue right now (besides the
length of the code and clearly the
inefficiency) is that I'm not sure how
to handle my rooms and workers inputs,
which are select forms. If the user
does not select a value, I want to
remove these filters from the process
server side. Should I just create two
separate conditional series of lookups
for these outcomes?
Q objects are only for complex lookups. I don't see a need for them here.
I also don't see why you need to chain the filters. I at first wondered if these are m2m, but these types of queries (__gt/__lt) don't behave any differently chaining as there is no overlap between the queries.
# this is more readable / concise.
# I'd combine as many of your queries as you can just for readability.
posts = Posts.objects.filter(
region__in=region,
cost__gte=min_cost,
# etc
)
Now, if you want optional arguments, my suggestion is to use a dictionary of keyword arguments so that you can dynamically populate the kwargs.
keyword_arguments = {
'region__in': region,
'cost__gte': min_cost,
'cost__lt': max_cost,
'availability__gt': date_min,
'availability__lt': date_max,
}
if request.GET.get('rooms'):
keyword_arguments['rooms'] = request.GET['rooms']
if request.GET.get('workers'):
keyword_arguments['workers'] = request.GET['workers']
posts = Posts.objects.filter(**keyword_arguments)
I'm trying to order a list of items in django by the number of comments they have. However, there seems to be an issue in that the Count function doesn't take into account the fact that django comments also uses a content_type_id to discern between comments for different objects!
This gives me a slight problem in that the comment counts for all objects are wrong using the standard methods; is there a 'nice' fix or do I need to drop back to raw sql?
Code to try and ge the correct ordering:
app_list = App.objects.filter(published=True)
.annotate(num_comments=Count('comments'))
.order_by('-num_comments')
Sample output from the query (note no mention of the content type id):
SELECT "apps_app"."id", "apps_app"."name",
"apps_app"."description","apps_app"."author_name", "apps_app"."site_url",
"apps_app"."source_url", "apps_app"."date_added", "apps_app"."date_modified",
"apps_app"."published", "apps_app"."published_email_sent", "apps_app"."created_by_id",
"apps_app"."rating_votes", "apps_app"."rating_score", COUNT("django_comments"."id") AS
"num_comments" FROM "apps_app" LEFT OUTER JOIN "django_comments" ON ("apps_app"."id" =
"django_comments"."object_pk") WHERE "apps_app"."published" = 1 GROUP BY
"apps_app"."id", "apps_app"."name", "apps_app"."description", "apps_app"."author_name",
"apps_app"."site_url", "apps_app"."source_url", "apps_app"."date_added",
"apps_app"."date_modified", "apps_app"."published", "apps_app"."published_email_sent",
"apps_app"."created_by_id", "apps_app"."rating_votes", "apps_app"."rating_score" ORDER
BY num_comments DESC LIMIT 4
Think I found the answer: Django Snippet
I'd like a URL of the form:
... field1/eq/value1/field2/gt/value2/ ...
Where I want to filter the contents of the page in the view function based on an arbitrary number of fields (the names of which are not known in advance).
I've tried:
(r'^((?P<field>\w+)/(?P<op>[a-z]+)/(?P<value>\w+)/)*$', my_view)
But the keyword arguments are filled with the last set of three field/op/value to occur in the URL.
Is there any way that I could populate a list or dictionary based on a variable number of URl fields like this?
Or should I be doing this some completely different way?
Don't do this.
Use the query string. ?field,eq,value&field,gt,value will work out much better.
I have some codes like this:
cats = Category.objects.filter(is_featured=True)
for cat in cats:
entries = Entry.objects.filter(score>=10, category=cat).order_by("-pub_date")[:10]
But, the results just show the last item of cats and also have problems with where ">=" in filter. Help me solve these problems. Thanks so much!
You may want to start by reading the django docs on this subject. However, just to get you started, the filter() method is just like any other method, in that it only takes arguments and keyword args, not expressions. So, you can't say foo <= bar, just foo=bar. Django gets around this limitation by allowing keyword names to indicate the relationship to the value you pass in. In your case, you would want to use:
Entry.objects.filter(score__gte=10)
The __gte appended to the field name indicates the comparison to be performed (score >= 10).
Your not appending to entries on each iteration of the for loop, therefore you only get the results of the last category. Try this:
entries = Entry.objects.filter(score__gte=10, category__is_featured=True).order_by("-pub_date")[:10]