Ansible with loops or lookup


Since Ansible version 2.5 there is a lot of discussion and confusion about the loop syntax. There is also discussion if with_…​: will be replaced by loop: deprecating the with_…​ keywords. Even Ansibles documentation is not clear about this.

Should I use loop: or with_…​:, in fact nobody really knows. What would the correct syntax be?

---
- name: Loops with with_ and lookup
  hosts: localhost
  connection: local
  gather_facts: no
  vars:
    people:
      - john
      - paul
      - mary
    drinks:
      - beer
      - wine
      - whisky

  tasks:
    - name: with nested
      debug:
        msg: "with_nested: item[0] is '{{ item[0] }}' and item[1] is '{{ item[1] }}'"
      with_nested:
        - "{{ people }}"
        - "{{ drinks }}"

    - name: nested and loop
      debug:
        msg: "nested_loop: item[0] is '{{ item[0] }}' and item[1] is '{{ item[1] }}'"
      loop:
        - "{{ people }}"
        - "{{ drinks }}"

The best indication for this would be the Migrating from with_X to loop section in the Ansible documentation.

But to be sure if a certain syntax works, I created a playbook that tests all (OK, not all but a lot) different syntaxes and show the output. Enjoy!

---
- name: Loops with with_ and lookup, query and others
  hosts: localhost
  connection: local
  gather_facts: no
  vars:
    beatles:
      john: guitar - vocals
      paul: bass - vocals
      ringo: drums - vocals
      george: guitar - vocals
    people:
      - john
      - paul
      - mary
    drinks:
      - beer
      - wine
      - whisky

  tasks:
    - name: with_items loop
      debug:
        msg: "with_items: item is '{{ item }}'"
      with_items: "{{ people }}"

    - name: with loop
      debug:
        msg: "loop: item is '{{ item }}'"
      loop: "{{ people }}"

    - name: with nested
      debug:
        msg: "with_nested: item[0] is '{{ item[0] }}' and item[1] is '{{ item[1] }}'"
      with_nested:
        - "{{ people }}"
        - "{{ drinks }}"

    - name: nested and loop
      debug:
        msg: "nested_loop: item[0] is '{{ item[0] }}' and item[1] is '{{ item[1] }}'"
      loop:
        - "{{ people }}"
        - "{{ drinks }}"

    # This example gives a Cartesian product of people with drinks. Way more than you want
    #- name: nested and lookup (this is wrong!!!)
    #  debug:
    #    msg: "with_nested_lookup: item[0] is '{{ item[0] }}' and item[1] is '{{ item[1] }}'"
    #  with_nested: "{{ lookup('nested', people, drinks, wantlist=True ) }}"

    - name: nested with loop and lookup
      debug:
        msg: "nested_loop_lookup: item[0] is '{{ item[0] }}' and item[1] is '{{ item[1] }}'"
      loop: "{{ lookup('nested', people, drinks, wantlist=True ) }}"

    - name: nested with loop and query
      debug:
        msg: "nested_loop_query: item[0] is '{{ item[0] }}' and item[1] is '{{ item[1] }}'"
      loop: "{{ query('nested', people, drinks ) }}"

    - name: with dict
      debug:
        msg: "with_dict: item.key is '{{ item.key }}' and item.value is '{{ item.value }}'"
      with_dict: "{{ beatles }}"

    - name: with dict lookup
      debug:
        msg: "with_dict_lookup: item.key is '{{ item.key }}' and item.value is '{{ item.value }}'"
      loop: "{{ lookup('dict', beatles) }}"

    - name: with dict query
      debug:
        msg: "with_dict_query: item.key is '{{ item.key }}' and item.value is '{{ item.value }}'"
      loop: "{{ query('dict', beatles) }}"

    - name: with dict2items
      debug:
        msg: "with_dict2items: item.key is '{{ item.key }}' and item.value is '{{ item.value }}'"
      loop: "{{ beatles | dict2items }}"

    - name: with sequence loop
      debug:
        msg: "with_sequence: item is '{{ item }}'"
      # end is inclusive of the end point
      with_sequence:
        start=0
        end=10
        stride=2
        format=guru_%02x

    - name: with sequence loop and lookup
      debug:
        msg: "sequence_lookup: item is '{{ item }}'"
      # end is inclusive of the end point
      loop: "{{ lookup('sequence', 'start=0 end=10 stride=2 format=guru_%02x', wantlist=True) }}"

    - name: with sequence loop and query
      debug:
        msg: "sequence_query: item is '{{ item }}'"
      # end is inclusive of the end point
      loop: "{{ query('sequence', 'start=0 end=10 stride=2 format=guru_%02x') }}"

    - name: with_sequence loop and range
      debug:
              msg: "loop_range: item is {{ 'guru_%02x' | format(item) }}"
      # range is exclusive of the end point
      loop: "{{ range(0, 10 + 1, 2) | list }}"

See also