Anurag Rana
Posted on August 14, 2019
Originally published at pythoncircle.com
Demo of the code used below: DjangoTemplateFiddle.com
For loop is used to iterate over any iterable object, accessing one item at a time and making it available inside the for loop body.
For example, if you want to create a drop down of countries in Django template, you can use the below code.
{% for country in country_list %}
<option name="{{country}}">{{country|title}}</option>
{% endfor %}
To iterate over a dictionary of people's name and their age, just like you would do in Python, use below code.
{% for name, age in data.items %}
Name: {{name}}, Age: {{age}} <br>
{% endfor %}
Checking if iterable used in for loop is empty:
Let's say you want to display new messages to logged-in user. You fetched all the new messages from the database and stored them in a list and passed to render function along with the template.
Now you can either check if the message list is empty or not and then display the message accordingly. Example:
{% if messages %}
{% for message in messages %}
{{ message }}<br>
{% endfor %}
{% else %}
<div>No new message for you</div>
{% endif %}
Or you can use {% empty %}
tag along with {% for %}
tag as below.
{% for message in messages %}
{{ message }}
{% empty %}
<div>No new message for you</div>
{% endfor %}
Break in Django for loop:
That might be a piece of bad news for you. There is no break statement in Django template For loop.
Depending on your requirement you can do one of the following.
Option 1 - Iterate over the whole list but do not perform any action if the condition is not matched.
For example, you are printing numbers from a list and you need to exit the list as soon as number 99 is encountered. Normally this would be done as below in Python.
for number in numbers:
if 99 == number:
break
print(number)
But there is no break statement in Django template For loop. You can achieve the same functionality (almost) as below.
{% set isBreak = False %}
{% for number in numbers %}
{% if 99 == number %}
{% set isBreak = true %}
{% endif %}
{% if isBreak %}
{# this is a comment. Do nothing. #}
{% else %}
<div>{{number}}</div>
{% endif %}
{% endfor %}
Option 2 - You can create your own custom template tag.
You can experiment with Django template or can create your own fiddle and share with others. Django Template Fiddle.
Posted on August 14, 2019
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