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Django. Lessons for beginners

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Django if Tag


If Statement

An if statement evaluates a variable and executes a block of code if the value is true.

Example

{% if greeting == 1 %}
  <h1>Hello</h1>
{% endif %} 
Run Example »

Elif

The elif keyword says "if the previous conditions were not true, then try this condition".

Example

{% if greeting == 1 %}
  <h1>Hello</h1>
{% elif greeting == 2 %}
  <h1>Welcome</h1>
{% endif %} 
Run Example »

Else

The else keyword catches anything which isn't caught by the preceding conditions.

Example

{% if greeting == 1 %}
  <h1>Hello</h1>
{% elif greeting == 2 %}
  <h1>Welcome</h1>
{% else %}
  <h1>Goodbye</h1>
{% endif %} 
Run Example »

Operators

The above examples uses the == operator, which is used to check if a variable is equal to a value, but there are many other operators you can use, or you can even drop the operator if you just want to check if a variable is not empty:

Example

{% if greeting %}
  <h1>Hello</h1>
{% endif %} 
Run Example »

==

Is equal to.

Example

{% if greeting == 2 %}
  <h1>Hello</h1>
{% endif %} 
Run Example »

!=

Is not equal to.

Example

{% if greeting != 1 %}
  <h1>Hello</h1>
{% endif %} 
Run Example »

<

Is less than.

Example

{% if greeting < 3 %}
  <h1>Hello</h1>
{% endif %} 
Run Example »

<=

Is less than or equal to.

Example

{% if greeting <= 3 %}
  <h1>Hello</h1>
{% endif %} 
Run Example »

>

Is greater than.

Example

{% if greeting > 1 %}
  <h1>Hello</h1>
{% endif %} 
Run Example »

>=

Is greater than, or equal to.

Example

{% if greeting >= 1 %}
  <h1>Hello</h1>
{% endif %} 
Run Example »

and

To check if more than one condition is true.

Example

{% if greeting == 1 and day == "Friday" %}
  <h1>Hello Weekend!</h1>
{% endif %} 
Run Example »

or

To check if one of the conditions is true.

Example

{% if greeting == 1 or greeting == 5 %}
  <h1>Hello</h1>
{% endif %} 
Run Example »

and/or

Combine and and or.

Example

{% if greeting == 1 and day == "Friday" or greeting == 5 %}
Run Example »

Parentheses are not allowed in if statements in Django, so when you combine and and or operators, it is important to know that parentheses are added for and but not for or.

Meaning that the above example is read by the interpreter like this:

{% if (greeting == 1 and day == "Friday") or greeting == 5 %}

in

To check if a certain item is present in an object.

Example

{% if 'Banana' in fruits %}
  <h1>Hello</h1>
{% else %}
  <h1>Goodbye</h1>
{% endif %} 
Run Example »

not in

To check if a certain item is not present in an object.

Example

{% if 'Banana' not in fruits %}
  <h1>Hello</h1>
{% else %}
  <h1>Goodbye</h1>
{% endif %} 
Run Example »

is

Check if two objects are the same.

This operator is different from the == operator, because the == operator checks the values of two objects, but the is operator checks the identity of two objects.

In the view we have two objects, x and y, with the same values:

Example

views.py:

from django.http import HttpResponse
from django.template import loader

def testing(request):
  template = loader.get_template('template.html')
  context = {
    'x': ['Apple', 'Banana', 'Cherry'],
    'y': ['Apple', 'Banana', 'Cherry'],
  }
  return HttpResponse(template.render(context, request))

The two objects have the same value, but is it the same object?

Example

{% if x is y %}
  <h1>YES</h1>
{% else %}
  <h1>NO</h1>
{% endif %}
Run Example »

Let us try the same example with the == operator instead:

Example

{% if x == y %}
  <h1>YES</h1>
{% else %}
  <h1>NO</h1>
{% endif %}
Run Example »

How can two objects be the same? Well, if you have two objects that points to the same object, then the is operator evaluates to true:

We will demonstrate this by using the {% with %} tag, which allows us to create variables in the template:

Example

{% with var1=x var2=x %}
  {% if var1 is var2 %}
    <h1>YES</h1>
  {% else %}
    <h1>NO</h1>
  {% endif %}
{% endwith %}
Run Example »

is not

To check if two objects are not the same.

Example

{% if x is not y %}
  <h1>YES</h1>
{% else %}
  <h1>NO</h1>
{% endif %} 
Run Example »


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