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 passing 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 boolean operators 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. One can use various boolean operators with Django If Template tag.
Syntax:
{% if variable boolean_operator value %}
// statements
{% endif %}
Example:
if tags may use and, or not to test a number of variables or to negate a given variable:
html
{% 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 %} |
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.
Boolean operators – Django template Tags Explanation
Illustration of How to use Boolean operators in Django templates using an Example. Consider a project named neveropen having an app named Lazyroar.
Refer to the following articles to check how to create a project and an app in Django.
Now create a view through which we will pass the context dictionary,
In Lazyroar/views.py,
Python3
# import Http Response from djangofrom django.shortcuts import render # create a functiondef Lazyroar_view(request): # create a dictionary context = { "data" : 99, } # return response return render(request, "Lazyroar.html", context) |
Create a url path to map to this view. In Lazyroar/urls.py,
Python3
from django.urls import path# importing views from views.pyfrom .views import Lazyroar_viewurlpatterns = [ path('', Lazyroar_view),] |
Create a template in templates/Lazyroar.html,
html
{% if data == 99 %}Value in data is : - {{ data }}{% else %}Data is empty{% endif%} |
Let’s check what is displayed on “/” are displayed in the template.
Boolean Operators
== operator
Equality. Example:
{% if somevar == "x" %}
This appears if variable somevar equals the string "x"
{% endif %}
!= operator
Inequality. Example:
{% if somevar != "x" %}
This appears if variable somevar does not equal the string "x",
or if somevar is not found in the context
{% endif %}
< operator
Less than. Example:
{% if somevar < 100 %}
This appears if variable somevar is less than 100.
{% endif %}
> operator
Greater than. Example:
{% if somevar > 0 %}
This appears if variable somevar is greater than 0.
{% endif %}
<= operator
Less than or equal to. Example:
{% if somevar <= 100 %}
This appears if variable somevar is less than 100 or equal to 100.
{% endif %}
>= operator
Greater than or equal to. Example:
{% if somevar >= 1 %}
This appears if variable somevar is greater than 1 or equal to 1.
{% endif %}
in operator
Contained within. This operator is supported by many Python containers to test whether the given value is in the container. The following are some examples of how x in y will be interpreted:
{% if "bc" in "abcdef" %}
This appears since "bc" is a substring of "abcdef"
{% endif %}
{% if "hello" in greetings %}
If greetings is a list or set, one element of which is the string
"hello", this will appear.
{% endif %}
{% if user in users %}
If users is a QuerySet, this will appear if user is an
instance that belongs to the QuerySet.
{% endif %}
not in operator
Not contained within. This is the negation of the in operator.
is operator
Object identity. Tests if two values are the same object. Example:
{% if somevar is True %}
This appears if and only if somevar is True.
{% endif %}
{% if somevar is None %}
This appears if somevar is None, or if somevar is not found in the context.
{% endif %}
is not operator
Negated object identity. Tests if two values are not the same object. This is the negation of the is operator. Example:
{% if somevar is not True %}
This appears if somevar is not True, or if somevar is not found in the
context.
{% endif %}
{% if somevar is not None %}
This appears if and only if somevar is not None.
{% endif %}
