Variable in Jinja2 For Loop

问题

We're trying to come up with a way to use ansible facts within jinja2 For Loops.

For example, I want to get all servers that belong to my memcached group as well as a group based on release (something like tag_release_dev or tag_release_prod). When I try to use {{ tt_release }} within the For Loop it evaluates {{ tt_release }} rather than the value of the variable. Is there a way to use a variable within the loop definition?

{% for host in groups["tag_function_mem"] | intersect(groups["tag_release_{{ tt_release }}"]) %}
  {{ host }}:11211
  {%- if not loop.last %},{% endif %}
  {%- if loop.last %}"{% endif %}
  {% endfor %}
{% endif %}

回答1:

it evaluates {{ tt_release }} rather than the value of the variable.

This is because you already are inside a expression. You can not nest expressions - and you don't need to.

What you want is to concatenate the string "tag_release_" and the variable tt_release. In Jinja2 concatenation is done with a +.

{% for host in groups["tag_function_mem"] | intersect(groups["tag_release_" + tt_release]) %}

来源：https://stackoverflow.com/questions/38212684/variable-in-jinja2-for-loop