twig if not empty code example

Example 1: twig is not empty

{% if not (varname is empty) %}
 	That's not empty.
{% endif %}

Example 2: twig is empty

{% if varname is empty %}
 	That's empty.
{% endif %}

Example 3: if variable is defined twig

{# defined works with variable names #}
{% if foo is defined %}
    ...
{% endif %}

{# and attributes on variables names #}
{% if foo.bar is defined %}
    ...
{% endif %}

{% if foo['bar'] is defined %}
    ...
{% endif %}