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C # tutorial
An if statement evaluates a variable and executes a block of code if the value is true
An if statement evaluates a variable and executes a block of code if the value is true.
{% if greeting == 1 %}
<h1>Hello</h1>
{% endif %} The elif keyword says "if the previous conditions were not true,
then try this condition".
{% if greeting == 1 %}
<h1>Hello</h1>
{% elif greeting == 2 %}
<h1>Welcome</h1>
{% endif %} The else keyword catches anything which isn't caught by the preceding conditions.
{% if greeting == 1 %}
<h1>Hello</h1>
{% elif greeting == 2 %}
<h1>Welcome</h1>
{% else %}
<h1>Goodbye</h1>
{% endif %} 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:
{% if greeting %}
<h1>Hello</h1>
{% endif %} Is equal to.
{% if greeting == 2 %}
<h1>Hello</h1>
{% endif %} Is not equal to.
{% if greeting != 1 %}
<h1>Hello</h1>
{% endif %} <
Is less than.
{% if greeting < 3 %}
<h1>Hello</h1>
{% endif %} Is less than, or equal to.
{% if greeting <= 3 %}
<h1>Hello</h1>
{% endif %} Is greater than.
{% if greeting > 1 %}
<h1>Hello</h1>
{% endif %} Is greater than, or equal to.
{% if greeting >= 1 %}
<h1>Hello</h1>
{% endif %} To check if more than one condition is true.
{% if greeting == 1 and day == "Friday" %}
<h1>Hello Weekend!</h1>
{% endif %} To check if one of the conditions is true.
{% if greeting == 1 or greeting == 5 %}
<h1>Hello</h1>
{% endif %} Combine and and
or.
{% if greeting == 1 and day == "Friday" or greeting == 5 %}
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 %}
To check if a certain item is present in an object.
{% if 'Banana' in fruits %}
<h1>Hello</h1>
{% else %}
<h1>Goodbye</h1>
{% endif %} To check if a certain item is not present in an object.
{% if 'Banana' not in fruits %}
<h1>Hello</h1>
{% else %}
<h1>Goodbye</h1>
{% endif %} 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:
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?
{% if x is y %}
<h1>YES</h1>
{% else %}
<h1>NO</h1>
{% endif %}Let us try the same example with the == operator instead:
{% if x == y %}
<h1>YES</h1>
{% else %}
<h1>NO</h1>
{% endif %}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:
{% with var1=x var2=x %}
{% if var1 is var2 %}
<h1>YES</h1>
{% else %}
<h1>NO</h1>
{% endif %}
{% endwith %}To check if two objects are not the same.
{% if x is not y %}
<h1>YES</h1>
{% else %}
<h1>NO</h1>
{% endif %}