mydict = {"key1":"value1", "key2":"value2"}
The regular way to lookup a dictionary value in a Django template is {{ mydict.key1 }}
, {{ mydict.key2 }}
. What if the key is a loop variable? ie:
{% for item in list %} # where item has an attribute NAME
{{ mydict.item.NAME }} # I want to look up mydict[item.NAME]
{% endfor %}
mydict.item.NAME
fails. How to fix this?
Write a custom template filter:
from django.template.defaulttags import register
...
@register.filter
def get_item(dictionary, key):
return dictionary.get(key)
(I use .get
so that if the key is absent, it returns none. If you do dictionary[key]
it will raise a KeyError
then.)
usage:
{{ mydict|get_item:item.NAME }}
Fetch both the key and the value from the dictionary in the loop:
{% for key, value in mydict.items %}
{{ value }}
{% endfor %}
I find this easier to read and it avoids the need for special coding. I usually need the key and the value inside the loop anyway.
You can't by default. The dot is the separator / trigger for attribute lookup / key lookup / slice.
Dots have a special meaning in template rendering. A dot in a variable name signifies a lookup. Specifically, when the template system encounters a dot in a variable name, it tries the following lookups, in this order: Dictionary lookup. Example: foo["bar"] Attribute lookup. Example: foo.bar List-index lookup. Example: foo[bar]
But you can make a filter which lets you pass in an argument:
https://docs.djangoproject.com/en/dev/howto/custom-template-tags/#writing-custom-template-filters
@register.filter(name='lookup')
def lookup(value, arg):
return value[arg]
{{ mydict|lookup:item.name }}
return value.get(arg)
because that would not throw a KeyError exception if the key is not present.
For me creating a python file named template_filters.py
in my App with below content did the job
# coding=utf-8
from django.template.base import Library
register = Library()
@register.filter
def get_item(dictionary, key):
return dictionary.get(key)
usage is like what culebrón said :
{{ mydict|get_item:item.NAME }}
register = Library()
? What does it do ?
django.template.base.Library
class. by register = Library()
we instantiate that class and use filter
function annotator inside it to reach our need.
I had a similar situation. However I used a different solution.
In my model I create a property that does the dictionary lookup. In the template I then use the property.
In my model: -
@property
def state_(self):
""" Return the text of the state rather than an integer """
return self.STATE[self.state]
In my template: -
The state is: {{ item.state_ }}
Environment: Django 2.2
Example code:
from django.template.defaulttags import register
@register.filter(name='lookup')
def lookup(value, arg):
return value.get(arg)
I put this code in a file named template_filters.py in my project folder named portfoliomgr
No matter where you put your filter code, make sure you have __init__.py in that folder Add that file to libraries section in templates section in your projectfolder/settings.py file. For me, it is portfoliomgr/settings.py
TEMPLATES = [
{
'BACKEND': 'django.template.backends.django.DjangoTemplates',
'DIRS': [os.path.join(BASE_DIR, 'templates')],
'APP_DIRS': True,
'OPTIONS': {
'context_processors': [
'django.template.context_processors.debug',
'django.template.context_processors.request',
'django.contrib.auth.context_processors.auth',
'django.contrib.messages.context_processors.messages',
],
'libraries':{
'template_filters': 'portfoliomgr.template_filters',
}
},
},
]
In your html code load the library {% load template_filters %}
Since I can't comment, let me do this in the form of an answer:
to build on culebrón's answer or Yuji 'Tomita' Tomita's answer, the dictionary passed into the function is in the form of a string, so perhaps use ast.literal_eval to convert the string to a dictionary first, like in this example.
With this edit, the code should look like this:
# code for custom template tag
@register.filter(name='lookup')
def lookup(value, arg):
value_dict = ast.literal_eval(value)
return value_dict.get(arg)
<!--template tag (in the template)-->
{{ mydict|lookup:item.name }}
env: django 2.1.7
view:
dict_objs[query_obj.id] = {'obj': query_obj, 'tag': str_tag}
return render(request, 'obj.html', {'dict_objs': dict_objs})
template:
{% for obj_id,dict_obj in dict_objs.items %}
<td>{{ dict_obj.obj.obj_name }}</td>
<td style="display:none">{{ obj_id }}</td>
<td>{{ forloop.counter }}</td>
<td>{{ dict_obj.obj.update_timestamp|date:"Y-m-d H:i:s"}}</td>
{{ dict_obj.obj.obj_name }}
is in this case equivalent to Python code dict_obj["obj"]["obj_name"]
, however, the question is about the equivalent of dict_obj[obj][obj_name]
.
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