if - 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, if else etc.
This article revolves about how to use if tag in Templates. The {% if %} tag evaluates a variable, and if that variable is “true” (i.e. exists, is not empty, and is not a false boolean value) the contents of the block are output.

Syntax

{% if variable %}
// statements
{% else %}
// statements
{% endif %}

Example

{% if athlete_list %}
    Number of athletes: {{ athlete_list|length }}
{% elif athlete_in_locker_room_list %}
    Athletes should be out of the locker room soon!
{% else %}
    No athletes.
{% endif %}

In the above, if athlete_list is not empty, the number of athletes will be displayed by the {{ athlete_list|length }} variable.

As one can see, the if tag may take one or several {% elif %} clauses, as well as an {% else %} clause that will be displayed if all previous conditions fail. These clauses are optional.

if – Django template Tags Explanation

Illustration of How to use if 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" : 99,
    }
    # 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,

{% if data %}
Value in data is : - {{ data }}
{% else %}
Data is empty
{% endif%}

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

{% else %}

Let’s check if {% else %} statement is working or not.
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" : False,
    }
    # return response
    return render(request, "geeks.html", context)

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

Advanced Usage

if tags may use and, or or not to test a number of variables or to negate a given variable:

{% if athlete_list and coach_list %}
    Both athletes and coaches are available.
{% endif %}

{% if not athlete_list %}
    There are no athletes.
{% endif %}

{% if athlete_list or coach_list %}
    There are some athletes or some coaches.
{% endif %}

{% if not athlete_list or coach_list %}
    There are no athletes or there are some coaches.
{% endif %}

{% if athlete_list and not coach_list %}
    There are some athletes and absolutely no coaches.
{% endif %}

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