How to extract one attribute from a list of dictionaries

[jean-christophe manciot]

Let's suppose the following list of dictionaries:

- domain_definition:

        - name: server11

          cluster: cluster1

          port: '8080'

        - name: server12

          cluster: cluster2

          port: '8090'

        - name: server21

          cluster: cluster3

          port: '9080'

        - name: server22

          cluster: cluster4

          port: '9090'

The aim is to extract all ```name: 'value'``` from ```domain_definition``` into a list:

        - name: server11

        - name: server12

        - name: server21

        - name: server22

I tried for instance the following:

- set_fact:

        domain_definition_names_list: "{{ ['name'] | 

                                 intersect(domain_definition.keys()|list) }}"

but it fails:

fatal: [localhost]: FAILED! => {

    "msg": "The task includes an option with an undefined variable. The error was: 'list object' has no attribute 'keys'...}

Any suggestion?

[jean-christophe manciot]

 I'm using:

- ansible 2.9.7

- python 3.8.2 

[Dick Visser]

just to make sure - this is a list of list of dictionaries.

If this is your source of truth, and you intend to have a list of dicts, then it could look like this:

domain_definition:

        - name: server11

          cluster: cluster1

          port: '8080'

        - name: server12

          cluster: cluster2

          port: '8090'

        - name: server21

          cluster: cluster3

          port: '9080'

        - name: server22

          cluster: cluster4

          port: '9090'

This will make a difference when manipulating the data.

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Dick Visser
Trust & Identity Service Operations Manager
GÉANT

[Dick Visser]

More accurately, the data structure you posted isn't a variable, it's an item from a "upper" list variable - which we don't know the name of.

An example:

---
- hosts: localhost
  connection: local
  gather_facts: no

  vars:

    domain_definition:
      - name: server11
        cluster: cluster1
        port: '8080'
      - name: server12
        cluster: cluster2
        port: '8090'
      - name: server21
        cluster: cluster3
        port: '9080'
      - name: server22
        cluster: cluster4
        port: '9090'

  tasks:
    - name: Keep names
      debug:
        msg: "{{ domain_definition | json_query('[*].{name: name}') }}"

Gives:

TASK [Keep names] **************************************************************
ok: [localhost] =>
  msg:

[jean-christophe manciot]

That's what I meant (just a typo in the structure).

 

 

[jean-christophe manciot]

Thanks. :-)

[SandeepK]

Can we give the same information in hosts file and still work?

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[Dick Visser]

what do you mean. Examples with code?

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Sent from a mobile device - please excuse the brevity, spelling and punctuation.

[jean-christophe manciot]

Yes, of course: you can define the variable anywhere, including in the hosts file.

There are 2 differences though:

• the precedence.
• the way the variables are defined: the inventory file is not a yaml file (ini format). Refer to this post for how to define your dictionary(ies) in the hosts file.

[Stefan Hornburg (Racke)]

On 4/24/20 10:01 AM, jean-christophe manciot wrote:
> Yes, of course: you can define the variable anywhere, including in the hosts file.
> There are 2 differences though:
>

> * the precedence
> <https://docs.ansible.com/ansible/latest/user_guide/playbooks_variables.html#variable-precedence-where-should-i-put-a-variable>.
> * the way the variables are defined: the inventory file is not a yaml file (ini format). Refer to this post
> <https://stackoverflow.com/questions/29856738/how-to-define-hash-dict-in-ansible-inventory-file> for how to define

> your dictionary(ies) in the hosts file.
>

The second statement is correct only if you refer to the host file (defaults to /etc/ansible/host). The inventory for
your playbook can be written completely in YAML.

Regards
Racke

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[SandeepK]

Thank you guys that helps!

On Friday, April 24, 2020 at 4:06:08 AM UTC-4, Stefan Hornburg (Racke) wrote:

On 4/24/20 10:01 AM, jean-christophe manciot wrote:
> Yes, of course: you can define the variable anywhere, including in the hosts file.
> There are 2 differences though:
>
>   * the precedence
>     <https://docs.ansible.com/ansible/latest/user_guide/playbooks_variables.html#variable-precedence-where-should-i-put-a-variable>.
>   * the way the variables are defined: the inventory file is not a yaml file (ini format). Refer to this post
>     <https://stackoverflow.com/questions/29856738/how-to-define-hash-dict-in-ansible-inventory-file> for how to define
>     your dictionary(ies) in the hosts file.
>

The second statement is correct only if you refer to the host file (defaults to /etc/ansible/host). The inventory for
your playbook can be written completely in YAML.

Regards
        Racke

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