Unsorted Tips Regarding Jinja

Jinja Tips

Setting variables from a loop

To set a variable from a loop, you can use the namespace object from Jinja. This is useful when you want to set a variable based on a condition in a loop.

Consider the following ansible example:

_jupyter_rhel_python_mapping:
  rhel:
    - os_major_version: "8"
      python_version: 3.6.15
    - os_major_version: "9"
      python_version: 3.9.21

You could set the py_version variable based on the os_major_version in the following way:

{%- set ns = namespace(py_version = 3.12) %}
{%  for release in _jupyter_rhel_python_mapping.rhel %}
  {% if release.os_major_version == ansible_distribution_major_version %}
    {% set ns.py_version = release.python_version  %}
  {% endif %}
{% endfor -%}

How to get a list of ips from multiple inventory groups

To get a list of IPs from multiple inventory groups, you can use the union filter along with map and extract to gather the IP addresses from the host variables.

ips: "{{ groups['cluster'] | union(groups['ecs_nodes']) | map('extract', hostvars) | map(attribute='ansible_default_ipv4.address') | list }}"

Explanation of the code:

• groups['cluster'] and groups['ecs_nodes'] are the inventory groups you want to combine.
• union combines the two groups into a single set.
• map('extract', hostvars) extracts the host variables for each host in the combined group.
• map(attribute='ansible_default_ipv4.address') retrieves the default IPv4 address for each host.
• list converts the result into a list.