The following parameters can be used to loop through an array / dictionary / list.

• loop (preferred)
• with_items
• with_list

IMPORTANT

When possible, Ansible recommends using the loop parameter, as the loop parameter is meant to supercede the with_items option.

In this example, the debug module and with_items parameter are used to loop over an array of fruit (a fruit loop!).

The loop parameters will, by default, use the {{ item }} variable for each item in the list. Or, the loop_control parameter with loop_var can be used to define your own variable for each item in the list.

- name: loop through items
  debug: 
    var: item
  with_items:
    - apple
    - banana
    - orange
    - grapes

Which should return the following.

TASK [loop through items] 
ok: [server1.example.com] => (item=apple) => {
    "item": "apple"
}
ok: [server1.example.com] => (item=banana) => {
    "item": "banana"
}
ok: [server1.example.com] => (item=orange) => {
    "item": "orange"
}
ok: [server1.example.com] => (item=grapes) => {
    "item": "grapes"
}

Better yet, the array can be defined. Here is how you would create an array of fruit using the vars plugin.

vars:
  fruit: 
    - apple
    - banana
    - orange
    - grapes

And here is one way to loop through a JSON array.

- name: loop through the 'fruit' array
  debug: 
    var: item
  loop: "{{ fruit }}"

with_items vs loop

Be aware that there are differences between the with_items and loop parameters. For example, the following would produce the same output as above.

- name: loop through the 'fruit' array
  debug: 
    var: item
  with_items:
    - [ apple, banana, orange, grapes ]

However, the loop parameter . . .

- name: loop through the 'fruit' array
  debug: 
    var: item
  loop:
    - [ apple, banana, orange, grapes ]

would produce the following.

TASK [loop through the 'fruit' array]
ok: [server1.example.com] => (item=['apple', 'banana', 'orange', 'grapes']) => {
    "msg": " ['apple', 'banana', 'orange', 'grapes']"
}

index_of

Or, the index_of module can be used to get the index number of an element in a list/array, to avoid looping through each element in the array, which can be useful in reducing the amount of output returned when looping through a large list.

---
- hosts: localhost
  gather_facts: false
  vars:
    fruit:
     - apple
     - banana
     - orange
     - grapes
  tasks:
  - debug:
      msg: "banana index number = {{ lookup('ansible.utils.index_of', fruit, 'regex', 'banana') }}"
...

Running this playbook should return the following.

ok: [localhost] => {
    "msg": "banana index number = 1"
}

register parameter

The register parameter is store the standard output (stdout), standard error (stderr) and return code (rc) of a command. In this example, the stdout/stderr/rc of the ps command will be stored in a variable named "out". 

- name: ps command
  shell: ps
  register: out

Here is how you would loop over the standard out of the ps command.

- name: loop through the ps command
  debug: 
    var: item
  with_items: "{{ out.stdout_lines }}"

Be aware that sometimes register will have JSON that contains the results array. Notice in this example that the results array contains two items, foo and bar.

ok: [localhost] => {
    "out": {
        "results": [
            "stdout": "foo",
            "stdout": "bar"
            ]
        ]
    }
}
 

In this scenario, you would need to loop through the results array.

- name: loop through the ps command
  debug: 
    var: item.stdout
  with_items: "{{ ps.results }}"

key value pairs

In this example, the loop parameter is used to loop over the food hash.

- name: loop through the 'food' hash
  debug: 
    var: item
  with_items:
    - { key: 'fruit', value: 'banana' }
    - { key: 'fruit', value: 'orange' }
    - { key: 'veggy', value: 'onion' }
    - { key: 'veggy', value: 'pepper' }

Which should return the following. Refer to Ansible - Loop through a hash for more details on looping over a hash.

TASK [loop through the 'food' hash] 
ok: [server1.example.com] => (item=apple) => {
    "msg": {
        "key": "fruit",
        "value": "apple"
    }
}
ok: [server1.example.com] => (item={'key': 'fruit', 'value': 'banana'}) => {
    "msg": {
        "key": "fruit",
        "value": "banana"
    }
}
ok: [server1.example.com] => (item={'key': 'veggy', 'value': 'onion'}) => {
    "msg": {
        "key": "veggy",
        "value": "onion"
    }
}
ok: [server1.example.com] => (item={'key': 'veggy', 'value': 'pepper'}) => {
    "msg": {
        "key": "veggy",
        "value": "pepper"
    }
}