We have to pay attention where we set Nunjucks variables because they are scoped

{% set animals = ['🐱', '🐶', '🐺'] %}

{% for item in animals %}
  {% set animal = item %}
{% endfor %}

{{ animal }}
{# animal -> ERROR #}
{# animal declared INSIDE the loop is NOT available #}

{% set animals = ['🐱', '🐶', '🐺'] %}

{# note this declaration #}
{% set animal = '' %}

{% for item in animals %}
  {% set animal = item %}
{% endfor %}

{{ animal }}
{# animal declared OUTSIDE the loop is available #}
{# animal -> 🐺 (last array item) #}

📚 More info

Twig docs - set variables