Hi I am using App Engine/Python to do a simple website. I have some trouble with a Django template problem.
In short, I want to use a "ShortName" to access a "LongName".
The soource code:
LongName={"so":"stackoverflow","su":"superuser"}
ShortName=['so','su']
Then I pass these two parameters to the templates.
In the template I write:
{% for aname in ShortName %}
{{ aname }} stands for {{ LongName.aname }},
{% endfor %}
The output is:
so stands for, su stands for
No error is given. The LongName.aname wont work.
I have no idea whats wrong.
This is trying to access LongName['aname'], not LongName[aname].
You might have to write a custom template tag/filter to get this to work. This Django bug (marked WONTFIX) has a simple implementation:
def get(d, key):
return d.get(key, '')
register.filter(get)
which you would use by
{{ LongName|get:aname }}
after adding it to your app (that SO answer shows how to do it on GAE).
You could also pre-make a variable to loop over in the view, by passing in
# in view
name_abbrevs = [(k, LongName[k]) for k in ShortName]
# in template
{% for short_name, long_name in name_abbrevs %}
{{ short_name }} stands for {{ long_name }}
{% endif %}
If you really don't want to add a template tag -- which isn't that bad! you just make one file! :) -- or pass in an extra variable, Vic's approach will let you do this without touching the Python files at all. As he mentions, it involves a lot of pointless iteration, but it'll work fine for small lists.
Django templates have a drawback here. I've been in the same situation before. What you have to do is iterate over all the keys in LongName, and check if the key you're looking for matches the ShortName. Here you go:
{% for aname in ShortName %}
{% for short_version, long_version in LongName %}
{% if aname == short_version %}
{{ aname }} stands for {{ long_version }},
{% endif %}
{% endfor %}
{% endfor%}
It's inefficient, and essentially a pointless O(n^2) mechanism. However, there's no better way in pure Django templates to refer to entries of a dict by a variable name.
Related
I have a context dictionary entry objectives that maps objective query objects to a list of tests that belong to that objective. Example code:
objectives = Objective.objects.filter(requirement=requirement)
context_dict["requirements"][requirement] = objectives
for objective in objectives:
tests = Test.objects.filter(objective=objective)
context_dict["objectives"][objective] = tests
In my django html template, I iterate over objectives and display them. I then want to iterate over the tests that belong to these objectives. When I do this:
{% for test in {{ objectives|get_item:objective }} %}
I get a TemplateSyntaxError: 'for' statements should use the format 'for x in y':
In the application/templatetags directory, I have:
from django.template.defaulttags import register
...
#register.filter
def get_item(dictionary, key):
return dictionary.get(key)
If instead I make {{ objectives|get_item:objective }} a JS variable, I see that it does indeed produce a list, which I should be able to iterate over. Of course, I can't mix JS variables and the django template tags, so this is only for debugging:
var tests = {{ objectives|get_item:objective }}
var tests = [<Test: AT399_8_1>, <Test: AT399_8_2>, <Test: AT399_8_3>, <Test: AT399_8_4>, <Test: AT399_8_5> '...(remaining elements truncated)...']
How do I iterate over this list in the django template tag?
You cannot user {{...}} inside the {%...%}
What you can try is changing your filter to an assignment tag and using that value in the loop
#register.assignment_tag
def get_item(dictionary, key):
return dictionary.get(key)
And then in your template use it as
{% get_item objectives objective as tests %}
{% for test in test %}
....
{% endfor %}
Instead of all this if your models are proper with foreign keys I would do something like
{% for objective in requirement.objective_set.all %}
{% for test in objective.test_set.all %}
....
{% endfor %}
{% endfor %}
In my context I would pass only the requirement
You already have an answer, but note that dropping the {{ }} tags and keeping everything else the same would have worked fine.
{% for test in objectives|get_item:objective %}
**This is Right Answer for Using Django if else and for loop **
Note :- We Have to Put Key in " " string (Double quotes) some time produce an error so That is good way bcz i faced that problem whwn i Learned
{% if 'numbers'|length > 0 %}
{% for i in numbers %}
{% if i > 20 %}
{{i}}
{% endif %}
{% endfor %}
{% else %}
Empty
{% endif %}
This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
Get list item dynamically in django templates
How to get list items with variable counter. The aim is to get the so item instead of list
not like this
{% for item in listModels %}
{{ item | safe }}
{% endfor %}
so work
{% for i in listModels|length|get_range %} // get size list
{{ listModels.i | safe }}
{% endfor %}
do not work
{% for i in listModels|length|get_range %} // get size list
{{ listModels.i | safe }}
{% endfor %}
Django templates will not allow you to do this. I'm not going to lecture you on keeping your logic out of your templates, because I think it's a stylistic choice. But understand that this is the easiest way. If you need to use the index, you can access it as a forloop property, as explained in the documentation.
If you really want variable indexing, you could make your own custom template tag to do it. But, in this case, I suggest you use a more powerful templating language, like Jinja2, instead of torturing the Django templating language.
Django Template Language provides you a way to do this...
{% for item in listModels %}
{{ forloop.counter }}
{% endfor %}
I fixed like I did the following:
{{ listModelsData|lookup:i|lookAttribute:"author" }} -// this equal listModelsData[i].author - this code in python
#register.filter
def lookAttribute (d, token):
return getattr (d, token)
When using Django templates, should I have some templates that act like "subroutines", so to speak, or should I generate HTML from within my code in these cases?
For example, I have a template with several lists of names, each of which I want to turn into a select. Should I have a template that renders the name_list variable into a select, and do something like this:
#in the view:
return {'name_list_1': name_list_1,
'name_list_2': name_list_2,
'name_list_3': name_list_3}
#in the template:
{% with name_list_1 as name_list %}
{% include "sub_name_list_select.html" %}
{% endwith %}
{% with name_list_2 as name_list %}
{% include "sub_name_list_select.html" %}
{% endwith %}
{% with name_list_3 as name_list %}
{% include "sub_name_list_select.html" %}
{% endwith %}
Or should I have a function in my code, name_list_to_select_html, which does the same job, and do this:
return {'name_list_1_html': name_list_to_select_html(name_list_1),
'name_list_2_html': name_list_to_select_html(name_list_2),
'name_list_3_html': name_list_to_select_html(name_list_3)}
#in the template:
{{ name_list_1_html|safe }}
{{ name_list_2_html|safe }}
{{ name_list_3_html|safe }}
Or are both of these wrong and I am getting the philosophy totally wrong?
Additional question: in terms of speed, is it slow to constantly include templates? Is that a bonus point for the in-code html generation?
Generally, HTML should only be generated in the templating system or directly related code. That keeps the view of the data completely separate from the business and functional logic. I feel that's a proper separation of concerns. Go with your first solution.
As for performance, Django should probably take around the same amount of time running either code. But it has built-in view and template fragment caching if you know those segments of code don't need to be regenerated on every request.
Is it possible to sort a set of related items in a DJango template?
That is: this code (with HTML tags omitted for clarity):
{% for event in eventsCollection %}
{{ event.location }}
{% for attendee in event.attendee_set.all %}
{{ attendee.first_name }} {{ attendee.last_name }}
{% endfor %}
{% endfor %}
displays almost exactly want I want. The only thing I want to change is I the list of attendees to be sorted by last name. I've tried saying something like this:
{% for event in events %}
{{ event.location }}
{% for attendee in event.attendee_set.order_by__last_name %}
{{ attendee.first_name }} {{ attendee.last_name }}
{% endfor %}
{% endfor %}
Alas, the above syntax doesn't work (it produces an empty list) and neither does any other variation I have thought of (lot's of syntax errors reported, but no joy).
I could, of course, produce some kind of array of sorted attendee lists in my view, but that is an ugly and fragile (and did I mention ugly) solution.
Needless to say, but I'll say it anyway, I have perused the on-line docs and searched Stack Overflow and the archives of django-user without finding anything helpful (ah, if only a query set were a dictionary dictsort would do the job, but it's not and it doesn't)
==============================================
Edited to add additional thoughts
after accepting Tawmas's answer.
Tawmas addressed the issue exactly as I presented it -- although the solution was not what I expected. As a result I learned a useful technique that can be used in other situations as well.
Tom's answer proposed an approach I had already mentioned in my OP and tentatively rejected as being "ugly".
The "ugly" was a gut reaction, and I wanted to clarify what was wrong with it. In doing so I realized that the reason it was an ugly approach was because I was hung up on the idea of passing a query set to the template to be rendered. If I relax that requirement, there is an un-ugly approach that should work.
I haven't tried this yet, but suppose that rather than passing the queryset, the view code iterated through the query set producing a list of Events, then decorated each Event with a query set for the corresponding attendees which WAS sorted (or filtered, or whatever) in the desired way. Something like so:
eventCollection = []
events = Event.object.[filtered and sorted to taste]
for event in events:
event.attendee_list = event.attendee_set.[filtered and sorted to taste]
eventCollection.append(event)
Now the template becomes:
{% for event in events %}
{{ event.location }}
{% for attendee in event.attendee_list %}
{{ attendee.first_name }} {{ attendee.last_name }}
{% endfor %}
{% endfor %}
The downside is the view has to "actualize" all of the events at once which could be a problem if there were large numbers of events. Of course one could add pagination, but that complicates the view considerably.
The upside is the "prepare the data to be displayed" code is in the view where it belongs letting the template focus on formatting the data provided by the view for display. This is right and proper.
So my plan is to use Tawmas' technique for large tables and the above technique for small
tables, with the definition of large and small left to the reader (grin.)
You can use template filter dictsort https://docs.djangoproject.com/en/dev/ref/templates/builtins/#std:templatefilter-dictsort
This should work:
{% for event in eventsCollection %}
{{ event.location }}
{% for attendee in event.attendee_set.all|dictsort:"last_name" %}
{{ attendee.first_name }} {{ attendee.last_name }}
{% endfor %}
{% endfor %}
You need to specify the ordering in the attendee model, like this. For example (assuming your model class is named Attendee):
class Attendee(models.Model):
class Meta:
ordering = ['last_name']
See the manual for further reference.
EDIT. Another solution is to add a property to your Event model, that you can access from your template:
class Event(models.Model):
# ...
#property
def sorted_attendee_set(self):
return self.attendee_set.order_by('last_name')
You could define more of these as you need them...
One solution is to make a custom templatag:
#register.filter
def order_by(queryset, args):
args = [x.strip() for x in args.split(',')]
return queryset.order_by(*args)
use like this:
{% for image in instance.folder.files|order_by:"original_filename" %}
...
{% endfor %}
regroup should be able to do what you want, but is there a reason you can't order them the way you want back in the view?
this is my code :
{% for i,j in enumerate(a) %}
{{i}} ,{{j}}
{% endfor%}
but , it show a error , i think it cant run the enumerate method ,
so how to run the enumerate in django template ,
thanks
The template subsystem has some special constructs built into the for/endfor block that allows you to access the current index of the loop without having to call enumerate.
{% for j in a %}
{{ forloop.counter0 }}, {{ j }}
{% endfor %}
While this snippet solves your immediate problem, if you're expecting to have access to Python builtins and other Python constructs inside your Django templates, you may be misunderstanding the sandbox that it provides/enforces.
you can use {{ forloop.counter }} or {{ forloop.counter0 }} for the same effect, the latter is 0-indexed, thus more like enumerate.
{% for item in a %}
{{ forloop.counter }}, {{ item }}
{% endfor %}
Link related
Django template makes up the presentation layer and are not meant for logic. From the docs
If you have a background in programming, or if you’re used to languages which mix programming code directly into HTML, you’ll want to bear in mind that the Django template system is not simply Python embedded into HTML. This is by design: the template system is meant to express presentation, not program logic.
Now to get the same functionality in Django, you will have to complete your logic in the views.
views.py
def my_view(request, ...):
....
enumerated_a = enumerate(a);
....
return render_to_response('my_template.html', {'enumerated_a ': enumerated_a }..)
Now enumerate function returns an enumerate object which is iterable.
my_template.html
{% for index, item in enumerated_a %}
{{ index }},{{ item }}
{% endfor %}
Although I think you can probably change it to an enumerated list and use it like that as well.
If however you need to use a function within a template, i suggest you create a filter or a tag instead. For reference, check out http://docs.djangoproject.com/en/1.2/howto/custom-template-tags/