如何在Django模板中使用“不是不是”？

Question

I want to customize the greeting on my homepage so it's whether:

When logged in and entered first name:

John! Where do you want to go?

else:

Where do you want to go?

This is my template:

 {% if user.is_authenticated and not firstname_of_logged_user == None%}
 <h1 class="text-center" id="extraglow">{{firstname_of_logged_user}}! where do 
 you want to go?</h1></label>
{%else%}
<h1 class="text-center" id="extraglow">where do you want to go?</h1></label>
                                {%endif%}

However, it doesn't seem to pick up the "not None" part because if the user is logged in but didn't enter first name it shows like this:

! where do you want to go?

and if I say:

firstname_of_logged_user is not None

it says an error:

Unused 'is' at end of if expression.

Seems like an easy thing but it's not working. What's wrong? Cheers!

Answer 1

You can use the != operator instead of not . However, things can be simplified even further to:

{% if user.is_authenticated and firstname_of_logged_user %}

The above will check whether or not firstname_of_logged_user is truthy in your template.

Answer 2

The if template tag has supported the is operator since Django 1.10 ( release notes ).

You can now do {% if x is None %} and {% if x is not None %} .

Answer 3

The is operator is not supported. Just use {% if var != None %} . This is not exactly the same but it will be sufficient for most cases.

See supported operators here .

If you actually want to use the is operator, you would have to implement it as a custom template tag.

For instance:

@register.filter
def is(lhs, rhs):
    return lhs is rhs

Thus you will be able to use it as:

{% if var1|is:var2 or not var3|is:var4 %}
    ...
{% else %}
    ...
{% endif %}