Django Template Ternary Operator
Question:
I was wondering if there was a ternary operator (condition ? true-value : false-value) that could be used in a Django template. I see there is a python one (true-value if condition else false-value) but I’m unsure how to use that inside a Django template to display the html given by one of the values. Any ideas?
Answers:
Why would you need a ternary operator within a template? {% if %} and {% else %} are all you need.
Or you could try the firstof tag:
{% firstof var1 var2 var3 %}
which outputs the first one of var1, var2 or var3 which evaluates to a True value.
You don’t. The Django {% if %} templatetag has only just started supporting ==, and, etc. {% if cond %}{% else %}{% endif %} is as compact as it gets for now.
I wonder if the python and/or trick would work?
condition and true_value or false_value
behaves a like the ternary operator – outputs true_value if condition evaluates to True, and false_value if not.
I’ve just implemented the ternary operator for Django as a tag, see https://github.com/alexei/django-template-extensions
You can use it as:
{% ?: exp1 exp2 exp3 %}
{% ?: exp1 exp2 %}
Or:
{% iif exp1 exp2 exp3 %}
{% iif exp1 exp2 %}
I figured out that it makes more sense than the yesno filter, even though it’s really not that Pythonic.
Just because they haven’t been mentioned here yet: the built in template tags default, and default_if_none can be useful in simple circumstances:
default
If value evaluates to False, uses the given default. Otherwise, uses the value.
For example:
{{ value|default:"nothing" }}
If value is “” (the empty string), the output will be nothing.
default_if_none
If (and only if) value is None, uses the given default. Otherwise, uses the >value.
Note that if an empty string is given, the default value will not be used. Use >the default filter if you want to fallback for empty strings.
For example:
{{ value|default_if_none:"nothing" }}
If value is None, the output will be the string “nothing”.
https://docs.djangoproject.com/en/1.9/ref/templates/builtins/#default
I was wondering if there was a ternary operator (condition ? true-value : false-value) that could be used in a Django template. I see there is a python one (true-value if condition else false-value) but I’m unsure how to use that inside a Django template to display the html given by one of the values. Any ideas?
Why would you need a ternary operator within a template? {% if %} and {% else %} are all you need.
Or you could try the firstof tag:
{% firstof var1 var2 var3 %}
which outputs the first one of var1, var2 or var3 which evaluates to a True value.
You don’t. The Django {% if %} templatetag has only just started supporting ==, and, etc. {% if cond %}{% else %}{% endif %} is as compact as it gets for now.
I wonder if the python and/or trick would work?
condition and true_value or false_value
behaves a like the ternary operator – outputs true_value if condition evaluates to True, and false_value if not.
I’ve just implemented the ternary operator for Django as a tag, see https://github.com/alexei/django-template-extensions
You can use it as:
{% ?: exp1 exp2 exp3 %}
{% ?: exp1 exp2 %}
Or:
{% iif exp1 exp2 exp3 %}
{% iif exp1 exp2 %}
I figured out that it makes more sense than the yesno filter, even though it’s really not that Pythonic.
Just because they haven’t been mentioned here yet: the built in template tags default, and default_if_none can be useful in simple circumstances:
default
If value evaluates to False, uses the given default. Otherwise, uses the value.
For example:
{{ value|default:"nothing" }}If value is “” (the empty string), the output will be nothing.
default_if_none
If (and only if) value is None, uses the given default. Otherwise, uses the >value.
Note that if an empty string is given, the default value will not be used. Use >the default filter if you want to fallback for empty strings.
For example:
{{ value|default_if_none:"nothing" }}If value is None, the output will be the string “nothing”.
https://docs.djangoproject.com/en/1.9/ref/templates/builtins/#default