# deferred evaluation (?) **URL:** \ **Category:** Ansible Project\ **Created:** [July 27, 2023, 8:22pm UTC](https://forum.ansible.com/t/deferred-evaluation/38270 "2023-07-27T20:22:38Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![utoddl](https://sea1.discourse-cdn.com/ansible/user_avatar/forum.ansible.com/utoddl/32/249_2.png) [@utoddl](https://forum.ansible.com/u/utoddl)\ **Post date:** [July 27, 2023, 8:22pm UTC](https://forum.ansible.com/t/deferred-evaluation/38270/1 "2023-07-27T20:22:38Z")
I’m trying to loop over a set of strings with ansible.builtin.debug, and I want to produce a three-part message for each string, like this: - name: Demo expressions ansible.builtin.debug: msg: - ‘{{ item }}’ - ‘_evaluate item as a Jinja2 expression_’ - ‘_like previous, but with “| bool” appended_’ loop: - “0” - “1” - “2” - “[‘aa’, ‘bb’, ‘cc’] | intersect([‘bb’, ‘cc’])” - “[‘aa’, ‘bb’, ‘cc’] | intersect([‘bb’, ‘cc’]) | length \> 0” The first part of the message should show the string, and it does. The second part somehow needs to show the result of evaluating the string as a Jinja2 expression. The third part is supposed to append “| bool” onto the string, evaluate _that_ as a Jinja2 expression, and show the result. I feel like there should be some way to do this with lookup(‘items’,…), but I’m having no luck. I’d appreciate any suggestions. Thanks, ---
**Author:** ![system](https://us1.discourse-cdn.com/ansible/original/1X/1882d9a01da5d8996a862359b0913cc568a39b84.svg) [@system](https://forum.ansible.com/u/system)\ **Post date:** [July 27, 2023, 8:51pm UTC](https://forum.ansible.com/t/deferred-evaluation/38270/2 "2023-07-27T20:51:59Z")
try the template lookup ---
**Author:** ![utoddl](https://sea1.discourse-cdn.com/ansible/user_avatar/forum.ansible.com/utoddl/32/249_2.png) [@utoddl](https://forum.ansible.com/u/utoddl)\ **Post date:** [July 27, 2023, 9:18pm UTC](https://forum.ansible.com/t/deferred-evaluation/38270/3 "2023-07-27T21:18:39Z")
I’m confused. The template lookup wants a [list of] file[s]. I’d rather not write these strings out to temp files just to get them templated. Or am I misinterpreting your suggestion? ---
**Author:** ![vbotka](https://sea1.discourse-cdn.com/ansible/user_avatar/forum.ansible.com/vbotka/32/359_2.png) [@vbotka](https://forum.ansible.com/u/vbotka)\ **Post date:** [July 27, 2023, 10:03pm UTC](https://forum.ansible.com/t/deferred-evaluation/38270/4 "2023-07-27T22:03:22Z")
post expected result ---
**Author:** ![utoddl](https://sea1.discourse-cdn.com/ansible/user_avatar/forum.ansible.com/utoddl/32/249_2.png) [@utoddl](https://forum.ansible.com/u/utoddl)\ **Post date:** [July 28, 2023, 12:54am UTC](https://forum.ansible.com/t/deferred-evaluation/38270/5 "2023-07-28T00:54:03Z")
Sure. Here’s a complete example where the debug task’s output msg contains exactly what I want. However, instead of each item being a 3-element list of strings, I want to pass in a single string, and use that string in various ways within the msg: expressions to accomplish the same thing. To be clear: as presented below, this problem isn’t worth solving. After all, there’s the playbook down below already! But that’s not the point. The point is to understand effective _run-time_ techniques to build strings containing Jinja2 expressions and have them evaluated. (“Templated” I guess is the verb rather than “evaluated,” but that feels backwards. In my brain, “to template” means to examine a sufficiently large set of outputs and create a template adequate to reproduce those outputs from reasonable inputs. But I digress.) Apparently it’s possible to write such strings to a file and use lookup(‘template’,tmpfilename), but there doesn’t seem to be the equivalent of lookup(‘template’,jinja2\_expression\_string). Not that I have found anyway. ```auto [utoddl@tango ansible]$ **cat deferred.yml** --- # deferred.yml - name: Deferred evaluation demo hosts: localhost gather_facts: false tasks: - name: Evaluate booleanness of various expressions ansible.builtin.debug: msg: - '{{ item.0 }}' - '{{ item.1 }}' - '{{ item.2 }}' loop: - [ "0", "{{ 0 }}", "{{ 0 | bool }}"] - [ "1", "{{ 1 }}", "{{ 1 | bool }}"] - [ "2", "{{ 2 }}", "{{ 2 | bool }}"] - ["['aa', 'bb', 'cc'] | intersect(['bb', 'cc'])", "{{ ['aa', 'bb', 'cc'] | intersect(['bb', 'cc']) }}", "{{ ['aa', 'bb', 'cc'] | intersect(['bb', 'cc']) | bool }}"] - ["['aa', 'bb', 'cc'] | intersect(['bb', 'cc']) | length > 0", "{{ ['aa', 'bb', 'cc'] | intersect(['bb', 'cc']) | length > 0 }}", "{{ ['aa', 'bb', 'cc'] | intersect(['bb', 'cc']) | length > 0 | bool }}"] [utoddl@tango ansible]$ **ansible-playbook deferred.yml** PLAY [Deferred evaluation demo] ************************************************************************* TASK [Evaluate booleanness of various expressions] ****************************************************** ok: [localhost] => (item=['0', '0', False]) => { "msg": [ "0", "0", false ] } ok: [localhost] => (item=['1', '1', True]) => { "msg": [ "1", "1", true ] } ok: [localhost] => (item=['2', '2', False]) => { "msg": [ "2", "2", false ] } ok: [localhost] => (item=["['aa', 'bb', 'cc'] | intersect(['bb', 'cc'])", ['bb', 'cc'], False]) => { "msg": [ "['aa', 'bb', 'cc'] | intersect(['bb', 'cc'])", [ "bb", "cc" ], false ] } ok: [localhost] => (item=["['aa', 'bb', 'cc'] | intersect(['bb', 'cc']) | length > 0", True, True]) => { "msg": [ "['aa', 'bb', 'cc'] | intersect(['bb', 'cc']) | length > 0", true, true ] } PLAY RECAP ********************************************************************************************** localhost : ok=1 changed=0 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0 ``` ---
**Author:** ![vbotka](https://sea1.discourse-cdn.com/ansible/user_avatar/forum.ansible.com/vbotka/32/359_2.png) [@vbotka](https://forum.ansible.com/u/vbotka)\ **Post date:** [July 28, 2023, 3:27am UTC](https://forum.ansible.com/t/deferred-evaluation/38270/6 "2023-07-28T03:27:31Z")
Create a template. For example, > cat create\_test.j2 {% for i in strings %} {{ i }} = {{ '{{' }} {{ i }} {{ '}}' }} {% endfor %} Then, the below playbook > cat pb.yml - hosts: localhost   tasks:     - template:         src: create\_test.j2         dest: /tmp/test.j2       vars:         strings:           - '0'           - '1'           - "['aa', 'bb', 'cc']|intersect(['bb', 'cc'])"           - "['aa', 'bb', 'cc']|intersect(['bb', 'cc'])|length \> 0"     - debug:         msg: "{{ lookup('template', '/tmp/test.j2') }}" gives abridged   msg: |-     0 = 0     1 = 1     ['aa', 'bb', 'cc']|intersect(['bb', 'cc']) = ['bb', 'cc']     ['aa', 'bb', 'cc']|intersect(['bb', 'cc'])|length \> 0 = True