Django templates: If false?
Solution 1:
For posterity, I have a few NullBooleanField
s and here's what I do:
To check if it's True
:
{% if variable %}True{% endif %}
To check if it's False
(note this works because there's only 3 values -- True/False/None):
{% if variable != None %}False{% endif %}
To check if it's None
:
{% if variable == None %}None{% endif %}
I'm not sure why, but I can't do variable == False
, but I can do variable == None
.
Solution 2:
Django 1.10 (release notes) added the is
and is not
comparison operators to the if
tag. This change makes identity testing in a template pretty straightforward.
In[2]: from django.template import Context, Template
In[3]: context = Context({"somevar": False, "zero": 0})
In[4]: compare_false = Template("{% if somevar is False %}is false{% endif %}")
In[5]: compare_false.render(context)
Out[5]: u'is false'
In[6]: compare_zero = Template("{% if zero is not False %}not false{% endif %}")
In[7]: compare_zero.render(context)
Out[7]: u'not false'
If You are using an older Django then as of version 1.5 (release notes) the template engine interprets True
, False
and None
as the corresponding Python objects.
In[2]: from django.template import Context, Template
In[3]: context = Context({"is_true": True, "is_false": False,
"is_none": None, "zero": 0})
In[4]: compare_true = Template("{% if is_true == True %}true{% endif %}")
In[5]: compare_true.render(context)
Out[5]: u'true'
In[6]: compare_false = Template("{% if is_false == False %}false{% endif %}")
In[7]: compare_false.render(context)
Out[7]: u'false'
In[8]: compare_none = Template("{% if is_none == None %}none{% endif %}")
In[9]: compare_none.render(context)
Out[9]: u'none'
Although it does not work the way one might expect.
In[10]: compare_zero = Template("{% if zero == False %}0 == False{% endif %}")
In[11]: compare_zero.render(context)
Out[11]: u'0 == False'
Solution 3:
I think this will work for you:
{% if not myvar %}
Solution 4:
You could write a custom template filter to do this in a half-dozen lines of code:
from django.template import Library
register = Library()
@register.filter
def is_false(arg):
return arg is False
Then in your template:
{% if myvar|is_false %}...{% endif %}
Of course, you could make that template tag much more generic... but this suits your needs specifically ;-)