Not even sure I'm stating the question correctly. Here's the situation. I have a queryset generated by accessing the foreign key relationship. Using the standard Blog/Entry models in the Django documentation, let's say I have selected a blog and now have a set of entries:
entries = Blog.objects.get(id=1).entry_set.all()
So we have some entries for the blog, possibly zero. I'd like to then say construct a calendar and indicate which days have blog entries. So my thinking is to iterate over list of days in the month or whatever, and check the entries queryset for an entry with that date. Question is, what is the best way to do this? My first thought was to do something like
dayinfo = [] # we will iterate over this in the template
for curday in month:
dayinfo.append({'day':curday, 'entry':entries.filter(day=curday)})
Problem is that the filter call returns a new queryset, and that generates a new sql call for each loop iteration. I just need to pluck the entry object from entries if it exists and stick it into my calendar. So what is the best way to do this? I did get this to work:
dayinfo.append({'day':day, 'entry':[e for e in entries if e.day == curday][0]})
That does not generate new sql calls. But it sure seems ugly.
Resist the urge to put everything on one line - I think the code would be cleaner with something like this:
from collections import defaultdict
calendar = defaultdict(list)
for entry in entries:
calendar[entry.day].append(entry)
The defaultdict part is simple but you might want to initialize it with all of the days in a month if you're just planning to use a for loop in the template. Also note that if you're using Django 1.1 you can use the new annotate() method to simply calculate the post count if you're not actually planning to generate links to individual posts.
Related
I'm learning about Django tables. I first wrote a basic example, here my view:
def people1(request):
table = PersonTable(Person.objects.filter(id=2))
RequestConfig(request).configure(table)
return render(request, 'people.html', {'table': table})
This way I've been able to easily display a table with a filter condition "filter(id=2))".
After that I found SingleTableView which is supposed to be an easier way to display database tables, as an example I wrote this view, which worked fine:
from django_tables2 import SingleTableView
class PersonList(SingleTableView):
template_name = 'ta07/comun.html'
model = Person
table_class = PersonTable
Questions are: how should I do to apply filters like in the first example? And is SingleTableView better than the basic way?
I'd say for now, you should only use it for the very basic use case. As soon as you need customizations from that, use your own.
Since filtering is a very common use case, I might consider adding that to the features of SingleTableView at some point. If you need it before that, feel free to open a pull request.
I currently have a public Google calendar that I am successfully pulling JSON data down using Google's API.
I am using HTTParty to convert the JSON to a ruby object.
response = HTTParty.get('http://www.google.com/calendar/feeds/colorado.edu_mdpltf14q21hhg50qb3e139fjg#group.calendar.google.com/public/full?alt=json&orderby=starttime&max-results=15&singleevents=true&sortorder=ascending&futureevents=true')
I want to retrieve many titles, event names, start times, end times ect. I can get these with commands like
response["feed"]["title"["$t"]
for the calendar's title, and
response["feed"]["entry"][0]["title"]["$t"]
for the event's title.
My question is two-fold. One, Is there a simpler way to pull this data? Two, how can I go about pulling multiple events information? I tried:
response.each do |x| response["feed"]["title"]["$t"]
but that spits out a no implicit conversion of string into integer error.
Based on your examples this should do it
response["feed"]["entry"].map {|entry| entry["title"]["$t"] }
response['feed']['entry'] is a simple array of hashes. It is probably best to extract that array to a temporary variable with
entries = response['feed']['entry']
thereafter your code it depends entirely on what you need to achieve. For instance, using the URL that you have provided
puts entries.length
shows
2
And
entries.each do |entry|
puts entry['title']['$t']
end
gives
NEW EVENT
Future EVENT
If we can help you to achieve something specific then please alter your answer or ask for clarification in a comment.
I have domain object named Roll and on the list page i want to show the user all the Roll objects iterating through a list, sorted by entry date.
Here is the code i am using
[rollList: Roll.findAll(sort:"rollDate"){userid==uid}]
rollDate is a field inside the Roll object with data type java.util.Date
Any suggestion on why the output is not sorted by rollDate. When i iterate through the rollList on the gsp page it is not sorted.
Also, on the Roll domain object i have even put this code, but it's still not sorting.
static mapping = {
sort "rollDate"
}
Thank you.
Why aren't you using the dynamic finders?
Roll.findAllByUserid( uid, [ sort:"rollDate", order: 'desc'] )
should work.
The findAll( Map, Closure ) method appeared not a long time ago, perhaps it was not tested well...
You might need to use order in your query as well, then add order to it
[rollList: Roll.findAll(sort:"rollDate", order: 'desc'){userid==uid}]
After trying both the solutions mentioned it still didn't work. So i thought something might be wrong on the front end.
While researching more i found that since i was using jquery data tables it used to re order the sorting. The solutions i found was here
jQuery DataTable rows order
So both the answers above are correct. The issue was actually with jquery data tables.
Currently I'm developing a debate module (much like a scrum/kanban board) for a GPL application (e-cidadania) and I don't have any experience with complex backends. I have developed a basic frontend for it, but now I don't know what approach I should use for the ajax and django backends to save and manipulate the table and notes.
The table can be N rows and N columns, every row and column has a name and position inside the table. Every note has also a position, text and comments (managed with the django comments framework).
I thought to store the parent element of every note (so I can place it later) and store the name of the rows and columns like CSV strings. Is that a good approach?
A screenshot of the current frontend: http: //ur1. ca/4zn4h
Update: I almost forgot, the frontend has been done with jQuery Sortables (so the user can move the note around as he likes) and CSS3.
You just need to model your domain (that is, debates that look like scrum boards) within Django. Think about it in plain English first, like this:
The has debates. These consist of criteria, organised in rows and columns in a specific order. This creates cells, which can have notes inside them.
Then you can set to work translating this into model classes. Don't worry too much about the fields they contain, the most important bit is the relationships (so the ForeignKey bits):
class Debate(models.Model):
title = ...
class Column(models.Model):
title = ...
order = ...
board = models.ForeignKey(ScrumBoard, related_name='columns')
class Row(models.Model):
title = ...
order = ...
board = models.ForeignKey(ScrumBoard, related_name='rows')
class Cell(models.Model):
column = models.ForeignKey(Column)
row = models.ForeignKey(Row)
class Note(models.Model)
text = ...
cell = models.ForeignKey(Cell)
That might be overly complex for what you need, though. I'm not an expert in the problem you're trying to solve? My suggestion, Django is quick – so start hacking, and give it a go, and if it's all wrong then you can go back a few steps, clean out your database and try again.
You might find it useful to play with South, which does database migrations for when you do things like add/remove/edit fields in your models.
There are two classes: User and Question
A user may have many questions, and it also contains a question_count
to record the the count of questions belong to him.
So, when I add a new question, I want update the question_count of the
user. At first, I do as:
question = Question(title='aaa', content='bbb')
Session.add(question)
Session.flush()
user = question.user
### user is not None
user.question_count += 1
Session.commit()
Everything goes well.
But I wan't to use event callback to do the same thing. As following:
from sqlalchemy.orm.interfaces import MapperExtension
class Callback(MapperExtension):
def after_insert(self, mapper, connection, instance):
user = instance.user
### user is None !!!
user.question_count += 1
class Question(Base):
__tablename__ = "questions"
__mapper_args__ = {'extension':Callback()}
....
Note in the "after_insert" method:
instance.user # -> Get None!!!
Why?
If I change that line to:
Session.query(User).filter_by(id=instance.user_id).one()
I can get the user successfully, But: the user can't be updated!
Look I have modified the user:
user.question_count += 1
But there is no 'update' sql printed in the console, and the
question_count are not updated.
I try to add Session.flush() or Session.commit() in the
after_insert() method, but both cause errors.
Is there any important thing I'm missing? Please help me, thank you
The author of sqlalchemy gave me an useful answer in a forum, I copy it here:
Additionally, a key concept of the
unit of work pattern is that it
organizes a full list of all
INSERT,UPDATE, and DELETE statements
which will be emitted, as well as the
order in which they are emitted,
before anything happens. When the
before_insert() and after_insert()
event hooks are called, this structure
has been determined, and cannot be
changed in any way. The
documentation for before_insert() and
before_update() mentions that the
flush plan cannot be affected at this
point - only individual attributes on
the object at hand, and those which
have not been inserted or updated yet,
can be affected here. Any scheme
which would like to change the flush
plan must use
SessionExtension.before_flush.
However, there are several ways of
accomplishing what you want here
without modifiying the flush plan.
The simplest is what I already
suggested. Use
MapperExtension.before_insert() on the
"User" class, and set
user.question_count =
len(user.questions). This assumes
that you are mutating the
user.questions collection, rather than
working with Question.user to
establish the relationship. If you
happened to be using a "dynamic"
relationship (which is not the case
here), you'd pull the history for
user.questions and count up what's
been appended and removed.
The next way, is to do pretty much
what you think you want here, that is
implement after_insert on Question,
but emit the UPDATE statement
yourself. That's why "connection" is
one of the arguments to the mapper
extension methods:
def after_insert(self, mapper, connection, instance):
connection.execute(users_table.update().\
values(question_count=users_table.c.question_count +1).\
where(users_table.c.id==instance.user_id))
I wouldn't prefer that approach since
it's quite wasteful for many new
Questions being added to a single
User. So yet another option, if
User.questions cannot be relied upon
and you'd like to avoid many ad-hoc
UPDATE statements, is to actually
affect the flush plan by using
SessionExtension.before_flush:
class
MySessionExtension(SessionExtension):
def before_flush(self, session, flush_context):
for obj in session.new:
if isinstance(obj, Question):
obj.user.question_count +=1
for obj in session.deleted:
if isinstance(obj, Question):
obj.user.question_count -= 1
To combine the "aggregate" approach of
the "before_flush" method with the
"emit the SQL yourself" approach of
the after_insert() method, you can
also use SessionExtension.after_flush,
to count everything up and emit a
single mass UPDATE statement with many
parameters. We're likely well in the
realm of overkill for this particular
situation, but I presented an example
of such a scheme at Pycon last year,
which you can see at
http://bitbucket.org/zzzeek/pycon2010/src/tip/chap5/sessionextension.py
.
And, as I tried, I found we should update the user.question_count in after_flush
user, being I assume a RelationshipProperty, is only populated after the flush (as it is only this point the ORM knows how to relate the two rows).
It looks like question_count is actually a derived property, being the number of Question rows for that user. If performance is not a concern, you could use a read-only property and let the mapper do the work:
#property
def question_count(self):
return len(self.questions)
Otherwise you're looking at implementing a trigger, either at the database-level or in python (which modifies the flush plan so is more complicated).