What is the equivalent of "none" in django templates?
PythonDjangoDjango FormsDjango TemplatesDjango ViewsPython Problem Overview
I want to see if a field/variable is none within a Django template. What is the correct syntax for that?
This is what I currently have:
{% if profile.user.first_name is null %}
<p> -- </p>
{% elif %}
{{ profile.user.first_name }} {{ profile.user.last_name }}
{% endif%}
In the example above, what would I use to replace "null"?
Python Solutions
Solution 1 - Python
None, False and True
all are available within template tags and filters. None, False
, the empty string ('', "", """"""
) and empty lists/tuples all evaluate to False
when evaluated by if
, so you can easily do
{% if profile.user.first_name == None %}
{% if not profile.user.first_name %}
A hint: @fabiocerqueira is right, leave logic to models, limit templates to be the only presentation layer and calculate stuff like that in you model. An example:
# someapp/models.py
class UserProfile(models.Model):
user = models.OneToOneField('auth.User')
# other fields
def get_full_name(self):
if not self.user.first_name:
return
return ' '.join([self.user.first_name, self.user.last_name])
# template
{{ user.get_profile.get_full_name }}
Hope this helps :)
Solution 2 - Python
You can also use another built-in template default_if_none
{{ profile.user.first_name|default_if_none:"--" }}
Solution 3 - Python
You can also use the built-in template filter default
:
If value evaluates to False (e.g. None, an empty string, 0, False); the default "--" is displayed.
{{ profile.user.first_name|default:"--" }}
Documentation: https://docs.djangoproject.com/en/dev/ref/templates/builtins/#default
Solution 4 - Python
is
operator : New in Django 1.10
{% if somevar is None %}
This appears if somevar is None, or if somevar is not found in the context.
{% endif %}
Solution 5 - Python
Solution 6 - Python
{% if profile.user.first_name %}
works (assuming you also don't want to accept ''
).
if
in Python in general treats None
, False
, ''
, []
, {}
, ... all as false.
Solution 7 - Python
Just a note about previous answers: Everything is correct if we want to display a string, but pay attention if you want to display numbers.
In particular when you have a 0 value bool(0)
evaluates to False
and so it will not display and probably is not what you want.
In this case better use
{% if profile.user.credit != None %}
Solution 8 - Python
You could try this:
{% if not profile.user.first_name.value %}
<p> -- </p>
{% else %}
{{ profile.user.first_name }} {{ profile.user.last_name }}
{% endif %}
This way, you're essentially checking to see if the form field first_name
has any value associated with it. See {{ field.value }}
in Looping over the form's fields in Django Documentation.
I'm using Django 3.0.