ansible Iterate var only if var is not empty - ansible

Question

I m trying to iterate over some variables in an ansible role. However, I want to ignore if the var is empty ex:ns3 from below code? I m trying when item length is greater than 0 but it seems not working? any ideas on how to do it?
---
- hosts: localhost
gather_facts: no
vars:
ns1: adm_analytics
ns2: adm_snap
ns3: ""
ns4: adm_eck
tasks:
- name: print namespace loop
with_items:
- "{{ ns1 }}"
- "{{ ns2 }}"
- "{{ ns3 }}"
- "{{ ns4 }}"
include_role:
name: verify_pod_status
vars:
NAMESPACE: "{{ item }}"
when: "{{ item | lenght > 0 }}"

Answer 1

You may have a look into the documentation about Conditionals.
There are some typos in your when clause.
---
- hosts: localhost
gather_facts: false
vars:
ns1: adm_analytics
ns2: adm_snap
ns3: ""
ns4: adm_eck
tasks:
- name: Print namespace loop
debug:
msg: "{{ item }}"
when: item | length > 0
with_items:
- "{{ ns1 }}"
- "{{ ns2 }}"
- "{{ ns3 }}"
- "{{ ns4 }}"
result into an output of
TASK [Print namespace loop] **************
ok: [localhost] => (item=adm_analytics) =>
msg: adm_analytics
ok: [localhost] => (item=adm_snap) =>
msg: adm_snap
ok: [localhost] => (item=adm_eck) =>
msg: adm_eck

Answer 2

when: condition is expanded by default. Fix the syntax
when: item|length > 0
Make your life easier and put the ns* variables into a dictionary. Then you can simply reference the values in the loop instead of listing the variables again. For example, the playbook
shell> cat playbook.yml
- hosts: localhost
gather_facts: no
vars:
ns:
ns1: adm_analytics
ns2: adm_snap
ns3: ""
ns4: adm_eck
tasks:
- name: print namespace loop
include_role:
name: verify_pod_status
loop: "{{ ns.values()|list }}"
vars:
NAMESPACE: "{{ item }}"
when: item|length > 0
and the role
shell> cat roles/verify_pod_status/tasks/main.yml
- debug:
var: NAMESPACE
give (abridged)
TASK [verify_pod_status : debug] ***********************************
skipping: [localhost] => (item=)
TASK [verify_pod_status : debug] ***********************************
ok: [localhost] =>
NAMESPACE: adm_analytics
TASK [verify_pod_status : debug] ***********************************
ok: [localhost] =>
NAMESPACE: adm_snap
TASK [verify_pod_status : debug] ***********************************
ok: [localhost] =>
NAMESPACE: adm_eck