Creating new list from values in list of dicts

[Rob White]

Hi all,

I am using the ec2_vpc_subnet_facts module to get back a list of subnet dicts.  I want to get the id from each of these dicts and add it to a new list so i end up with just a list of subnet ids.  I thought this might be possible with existing jinja filters but i'm not sure where to start so any pointers would be appreciated.

Example:

'subnets': [{u'availability_zone': u'ap-southeast-2a', u'tags': {u'Type': u'public', u'Zone': u'a', u'Env': u'support', u'Name': u'support-public-a'}, u'default_for_az': u'false', u'state': u'available', u'vpc_id': u'vpc-11223344', u'cidr_block': u'10.66.128.0/25', u'available_ip_address_count': 113, u'id': u'subnet-11223344', u'map_public_ip_on_launch': u'false'}, {u'availability_zone': u'ap-southeast-2b', u'tags': {u'Type': u'public', u'Zone': u'b', u'Env': u'support', u'Name': u'support-public-b'}, u'default_for_az': u'false', u'state': u'available', u'vpc_id': u'vpc-11223344', u'cidr_block': u'10.66.129.0/25', u'available_ip_address_count': 118, u'id': u'subnet-55667788', u'map_public_ip_on_launch': u'false'}]

I want to get each subnet.id in to a list so i end up with...

my_list: [subnet-11223344, subnet-55667788]

Thanks,

[Rob White]

So I wrote my own filter for this...

def idfromlistofdicts(l):
    result = []
    for item in l:
        result.append(item['id'])


    return result


class FilterModule(object):
    def filters(self):
        return {
            'idfromlistofdicts': idfromlistofdicts,
        }

Not sure if something like this already exists though.

[Takeshi Yaegashi]

Hello,

Try the following playbook:

---

- hosts: all

  gather_facts: no

  vars:

    subnets: [ { id: subnet-11223344 }, { id: subnet-55667788 } ]

    my_list: |

      {%- set o = [] %}

      {%- for i in subnets %}

      {%-   if o.append(i.id) %}

      {%-   endif %}

      {%- endfor %}

      {{ o }}

  tasks:

    - debug:

        var: my_list

Sample session:

$ ansible-playbook -i localhost, playbook.yml

PLAY [all] ******************************************************************** 

TASK: [debug ] **************************************************************** 

ok: [localhost] => {

    "var": {

        "my_list": [

            "subnet-11223344", 

            "subnet-55667788"

        ]

    }

}

PLAY RECAP ******************************************************************** 

localhost                  : ok=1    changed=0    unreachable=0    failed=0   

Regards,

--  

YAEGASHI Takeshi <yaeg...@debian.org>