for… пустой цикл - Теги шаблона Django

Опубликовано: 24 Февраля, 2022

A Django template is a text document or a Python string marked-up using the Django template language. Django being a powerful Batteries included framework provides convenience to rendering data in a template. Django templates not only allow paassing data from view to template, but also provides some limited features of a programming such as variables, for loops, comments, extends etc.
This article revolves about how to use for tag with empty in Templates. for tag loops over each item in an array, making the item available in a context variable. The for tag can take an optional {% empty %} clause whose text is displayed if the given array is empty or could not be found. This is basically used as a condition to be followed to check if queryset is empty and what action to be performed in the same scenario.

Syntax

{% for i in list %}
// Do this in non - empty condition
{% empty %}
// Do this in empty condition
{% endfor %}

Example

For example, to display a list of athletes provided in athlete_list:

<ul>
{% for athlete in athlete_list %}
    <li>{{ athlete.name }}</li>
{% empty %}
    <li>Sorry, no athletes in this list.</li>
{% endfor %}
</ul>

The above is equivalent to – but shorter, cleaner, and possibly faster than – the following:

<ul>
  {% if athlete_list %}
    {% for athlete in athlete_list %}
      <li>{{ athlete.name }}</li>
    {% endfor %}
  {% else %}
    <li>Sorry, no athletes in this list.</li>
  {% endif %}
</ul>

for … empty – Django template Tags Explanation

Illustration of How to use for …empty tag in Django templates using an Example. Consider a project named geeksforgeeks having an app named geeks.

Refer to the following articles to check how to create a project and an app in Django.
How to Create a Basic Project using MVT in Django?
How to Create an App in Django ?

Now create a view through which we will pass the context dictionary,
In geeks/views.py,

# import Http Response from django
from django.shortcuts import render
  
# create a function
def geeks_view(request):
    # create a dictionary
    context = {
        "data" : [1, 2, 3, 4, 5, 6, 7, 8, 9, 10],
    }
    # return response
    return render(request, "geeks.html", context)

Create a url path to map to this view. In geeks/urls.py,

from django.urls import path
  
# importing views from views.py
from .views import geeks_view
  
urlpatterns = [
    path("", geeks_view),
]

Create a template in templates/geeks.html,

{% for i in data %}
    <div class="row">
        {{ i }}
    </div>
{% endfor %}

Let’s check what is displayed on “/” are displayed in the template.

Anything enclosed between for tag would be repeated, the number of times the loop is run.

Now let’s pass an empty array and use empty tag along with for tag.
In geeks/views.py,

# import Http Response from django
from django.shortcuts import render
   
# create a function
def geeks_view(request):
    # create a dictionary
    context = {
        "data" : [],
    }
    # return response
    return render(request, "geeks.html", context)

Now in templates/geeks.html,

{% for i in data %}
    <div class="row">
        {{ i }}
    </div>
    {% empty %}
    <h4>There is nothing in this list</h4>
{% endfor %}

Now, check http://127.0.0.1:8000/,

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for… пустой цикл - Теги шаблона Django

Syntax

Example

for … empty – Django template Tags Explanation

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